: Yodl 4.05.02
: Frank B. Brokken (f.b.brokken@rug.nl)

        initially by Karel Kubat
Center for Information Technology, University of Groningen
: 1996-NOW

 
    Yodl is a package implementing a pre-document language and tools to
process it.  The idea of Yodl is that you write up a document in a
pre-language, then use the tools (e.g. yodl2html) to convert it to some final
document language.  Current converters are for HTML, man, LaTeX, a poor-man's
text converter and an experimental XML converter.  Main document types are
`article', `report', `book', `letter' and `manpage'.  The Yodl document
language is designed to be easy to use and extensible.
    

Table of Contents

Chapter 1: Introduction
1.1: What's new since version 4.00.00?
1.2: Why use Yodl?
1.3: Copying Yodl
Chapter 2: Yodl User Guide
2.1: Using the yodl program
2.2: The Yodl grammar
2.2.1: Language elements
2.2.1.1: Identifiers and Names
2.2.1.2: Numbers
2.2.1.3: Arguments to builtin functions and macros
2.2.1.4: Builtin functions
2.2.1.5: Character translation tables
2.2.1.6: Counters
2.2.1.7: Macros
2.2.1.8: Nousermacros
2.2.1.9: Symbols
2.2.2: Line continuation
2.2.3: The +identifier sequence
2.2.4: Preventing macros from being expanded
2.3: Character tables
2.3.1: Defining character tables
2.3.2: Using character tables
2.3.3: Pushing and popping character tables
2.4: Sending literal text to the output
2.5: Counters
2.5.1: Creating counters
2.5.2: Using counters
Chapter 3: All builtin functions
3.1: Yodl's builtin commands
3.1.1: ADDTOCOUNTER
3.1.2: ADDTOSYMBOL
3.1.3: ATEXIT
3.1.4: CHAR
3.1.5: CHDIR
3.1.6: COMMENT
3.1.7: COUNTERVALUE
3.1.8: DECWSLEVEL
3.1.9: DEFINECHARTABLE
3.1.10: DEFINECOUNTER
3.1.11: DEFINEMACRO
3.1.12: DEFINESYMBOL
3.1.13: DELETECHARTABLE
3.1.14: DELETECOUNTER
3.1.15: DELETEMACRO
3.1.16: DELETENOUSERMACRO
3.1.17: DELETESYMBOL
3.1.18: ERROR
3.1.19: EVAL
3.1.20: FILENAME
3.1.21: FPUTS
3.1.22: IFBUILTIN
3.1.23: IFCHARTABLE
3.1.24: IFDEF
3.1.25: IFEMPTY
3.1.26: IFEQUAL
3.1.27: IFGREATER
3.1.28: IFMACRO
3.1.29: IFSMALLER
3.1.30: IFSTREQUAL
3.1.31: IFSTRSUB
3.1.32: IFSYMBOL
3.1.33: IFZERO
3.1.34: INCLUDEFILE
3.1.35: INCWSLEVEL
3.1.36: INTERNALINDEX
3.1.37: NOEXPAND
3.1.38: NOEXPANDINCLUDE
3.1.39: NOEXPANDPATHINCLUDE
3.1.40: NOTRANS
3.1.41: NOUSERMACRO
3.1.42: OUTBASE
3.1.43: OUTDIR
3.1.44: OUTFILENAME
3.1.45: PARAGRAPH
3.1.46: PIPETHROUGH
3.1.47: POPCHARTABLE
3.1.48: POPCOUNTER
3.1.49: POPMACRO
3.1.50: POPSUBST
3.1.51: POPSYMBOL
3.1.52: POPWSLEVEL
3.1.53: PUSHCHARTABLE
3.1.54: PUSHCOUNTER
3.1.55: PUSHMACRO
3.1.56: PUSHSUBST
3.1.57: PUSHSYMBOL
3.1.58: PUSHWSLEVEL
3.1.59: RENAMEMACRO
3.1.60: SETCOUNTER
3.1.61: SETSYMBOL
3.1.62: SUBST
3.1.63: SYMBOLVALUE
3.1.64: SYSTEM
3.1.65: TYPEOUT
3.1.66: UPPERCASE
3.1.67: USECHARTABLE
3.1.68: USECOUNTER
3.1.69: VERBOSITY
3.1.70: WARNING
Chapter 4: Macros and Document types
4.1: General structure of a Yodl document
4.1.1: Document types
4.1.2: The manpage document type
4.2: Predefined macros
4.2.1: abstract(text)
4.2.2: addntosymbol(symbol)(n)(text)
4.2.3: affiliation(site)
4.2.4: AfourEnlarged()
4.2.5: appendix()
4.2.6: article(title)(author)(date)
4.2.7: attrib(text)
4.2.8: attribclear()
4.2.9: attribinsert()
4.2.10: bf(text)
4.2.11: bind(text)
4.2.12: book(title)(author)(date)
4.2.13: cell(contents)
4.2.14: cells(nColumns)(contents)
4.2.15: cellsline(from)(count)
4.2.16: center(text)
4.2.17: chapter(title)
4.2.18: cindex()
4.2.19: cite(text)
4.2.20: clearpage()
4.2.21: code(text)
4.2.22: columnline(from)(through)
4.2.23: dashes()
4.2.24: def(macroname)(nrofargs)(redefinition)
4.2.25: description(list)
4.2.26: dit(itemname)
4.2.27: eit()
4.2.28: ellipsis()
4.2.29: em(text)
4.2.30: email(address)
4.2.31: enumeration(list)
4.2.32: euro()
4.2.33: evalsymbol(symbol)(expression)
4.2.34: fig(label)
4.2.35: figure(file)(caption)(label)
4.2.36: file(text)
4.2.37: findex()
4.2.38: footnote(text)
4.2.39: gagmacrowarning(name name ...)
4.2.40: getaffilstring()
4.2.41: getauthorstring()
4.2.42: getchapterstring()
4.2.43: getdatestring()
4.2.44: getfigurestring()
4.2.45: getpartstring()
4.2.46: gettitlestring()
4.2.47: gettocstring()
4.2.48: htmlcommand(cmd)
4.2.49: htmlheadfile(file)
4.2.50: htmlheadopt(option)
4.2.51: htmlnewfile()
4.2.52: htmlstyle(tag)(definition)
4.2.53: htmlstylesheet(url)
4.2.54: htmltag(tagname)(start)
4.2.55: ifnewparagraph(truelist)(falselist)
4.2.56: includefile(file)
4.2.57: includeverbatim(file)
4.2.58: it()
4.2.59: itdesc(itemname)(contents)
4.2.60: itemization(list)
4.2.61: kindex()
4.2.62: label(labelname)
4.2.63: langle()
4.2.64: languagedutch()
4.2.65: languageenglish()
4.2.66: languageportugese()
4.2.67: LaTeX()
4.2.68: latexaddlayout(arg)
4.2.69: latexcommand(cmd)
4.2.70: latexdocumentclass(class)
4.2.71: latexlayoutcmds(NOTRANSs)
4.2.72: latexoptions(options)
4.2.73: latexpackage(options)(name)
4.2.74: lchapter(label)(title)
4.2.75: letter(language)(date)(subject)(opening)(salutation)(author)
4.2.76: letteraddenda(type)(value)
4.2.77: letteradmin(yourdate)(yourref)
4.2.78: letterfootitem(name)(value)
4.2.79: letterreplyto(name)(address)(zip city)
4.2.80: letterto(element)
4.2.81: link(description)(labelname)
4.2.82: lref(description)(labelname)
4.2.83: lsect(label)(title)
4.2.84: lsubsect(label)(title)
4.2.85: lsubsubsect(label)(title)
4.2.86: lsubsubsubsect(label)(title)
4.2.87: lurl(locator)
4.2.88: mailto(address)
4.2.89: makeindex()
4.2.90: mancommand(cmd)
4.2.91: manpage(title)(section)(date)(source)(manual)
4.2.92: manpageauthor()
4.2.93: manpagebugs()
4.2.94: manpagedescription()
4.2.95: manpagediagnostics()
4.2.96: manpagefiles()
4.2.97: manpagename(name)(short description)
4.2.98: manpageoptions()
4.2.99: manpagesection(SECTIONNAME)
4.2.100: manpageseealso()
4.2.101: manpagesynopsis()
4.2.102: manttquoted(onOff)
4.2.103: mbox()
4.2.104: metaC(text)
4.2.105: metaCOMMENT(text)
4.2.106: mscommand(cmd)
4.2.107: nbsp(count)
4.2.108: nchapter(title)
4.2.109: nemail(name)(address)
4.2.110: nl()
4.2.111: nodeprefix(text)
4.2.112: nodeprefix(text)
4.2.113: nodetext(text)
4.2.114: nohtmlfive()
4.2.115: nohtmlimgstyle()
4.2.116: nop(text)
4.2.117: nosloppyhfuzz()
4.2.118: notableofcontents()
4.2.119: notitleclearpage()
4.2.120: notocclearpage()
4.2.121: notransinclude(filename)
4.2.122: noxlatin()
4.2.123: nparagraph(title)
4.2.124: npart(title)
4.2.125: nsect(title)
4.2.126: nsubsect(title)
4.2.127: nsubsubsect(title)
4.2.128: nsubsubsect(title)
4.2.129: PageEnlarged(up)(height)(left)(width)
4.2.130: paragraph(title)
4.2.131: part(title)
4.2.132: pindex()
4.2.133: plainhtml(title)
4.2.134: printindex()
4.2.135: quote(text)
4.2.136: rangle()
4.2.137: redef(macro)(nrofargs)(redefinition)
4.2.138: redefinemacro(macro)(nrofargs)(redefinition)
4.2.139: ref(labelname)
4.2.140: report(title)(author)(date)
4.2.141: roffcmd(dotcmd)(sameline)(secondline)(thirdline)
4.2.142: row(contents)
4.2.143: rowline()
4.2.144: sc(text)
4.2.145: sect(title)
4.2.146: setaffilstring(name)
4.2.147: setauthorstring(name)
4.2.148: setchapterstring(name)
4.2.149: setdatestring(name)
4.2.150: setfigureext(name)
4.2.151: setfigurestring(name)
4.2.152: sethtmlfigureext(ext)
4.2.153: htmlmetacharset(meta-charset)
4.2.154: setincludepath(name)
4.2.155: setlanguage(name)
4.2.156: setlatexalign(alignment)
4.2.157: setlatexfigureext(ext)
4.2.158: setlatexverbchar(char)
4.2.159: setmanalign(alignment)
4.2.160: setpartstring(name)
4.2.161: setrofftab(x)
4.2.162: setrofftableoptions(optionlist)
4.2.163: settitlestring(name)
4.2.164: settocstring(name)
4.2.165: sgmlcommand(cmd)
4.2.166: sgmltag(tag)(onoff)
4.2.167: sloppyhfuzz(points)
4.2.168: standardlayout()
4.2.169: strong(contents)
4.2.170: subs(text)
4.2.171: subsect(title)
4.2.172: subsubsect(title)
4.2.173: subsubsubsect(title)
4.2.174: sups(text)
4.2.175: table(nColumns)(alignment)(Contents)
4.2.176: tableatt(nColumns)(alignment)(Contents)
4.2.177: tac(alignment)(contents)
4.2.178: tao(type)(specification)
4.2.179: tbl(align)(contents)
4.2.180: tc(contents)
4.2.181: tcell(text)
4.2.182: telycommand(cmd)
4.2.183: TeX()
4.2.184: texinfocommand(cmd)
4.2.185: tindex()
4.2.186: titleclearpage()
4.2.187: tline(beginNr)(endNr)
4.2.188: tnac(nCells)(alignment)(contents)
4.2.189: tnc(nCells)(contents)
4.2.190: tocclearpage()
4.2.191: tr(contents)
4.2.192: tt(text)
4.2.193: ttbegin()
4.2.194: ttend()
4.2.195: twrap(value)
4.2.196: txtcommand(cmd)
4.2.197: url(description)(locator)
4.2.198: verb(text)
4.2.199: verbinclude(filename)
4.2.200: verbinsert(args)
4.2.201: verborg(text)
4.2.202: verbpipe(command)(text)
4.2.203: vindex()
4.2.204: whenhtml(text)
4.2.205: whenlatex(text)
4.2.206: whenman(text)
4.2.207: whenms(text)
4.2.208: whensgml(text)
4.2.209: whentely(text)
4.2.210: whentexinfo(text)
4.2.211: whentxt(text)
4.2.212: whenxml(text)
4.2.213: xit(itemname)
4.2.214: xmlcommand(cmd)
4.2.215: xmlmenu(order)(title)(menulist)
4.2.216: xmlnewfile()
4.2.217: xmlsetdocumentbase(name)
4.2.218: xmltag(tag)(onoff)
4.3: Conversion-related topics
4.3.1: Conversion-type specific literal commands
4.3.2: Figures
4.3.3: Fonts and sizes
4.3.4: Labels, links, references and URLs
4.3.5: Lists and environments
4.3.5.1: National language support
4.3.5.2: Pagebreaks after the title and table of contents
4.3.6: Sectioning
4.3.7: Typesetting modifiers
4.3.8: Miscellaneous commands
4.4: Locations of the macros
Chapter 5: Conversions and converters
5.1: Conversion script invocations
5.2: The HTML converter
5.2.0.1: Direct commands to HTML
5.2.0.2: Section numbering
5.3: The LaTeX converter
5.3.0.1: Direct commands to LaTeX
5.3.0.2: Verbatim text
5.4: The man converter
5.4.0.1: Direct commands to man
5.5: The txt converter
5.5.0.1: Direct commands to txt
5.6: The experimental XML converter
5.7: The Yodl Post-processor `yodlpost'
5.8: The support program `yodlverbinsert'
5.8.1: Example
Chapter 6: Technical information
6.1: Obtaining Yodl
6.1.1: Installing Yodl
6.2: Organization of the software
6.2.1: Subdirectories and their meanings
6.3: Yodl's component interrelations and component setup
6.4: The token-producer `lexer_lex()'
6.5: The Parser's Finite State Automaton
6.6: Adding a new macro
6.7: The Yodl post-processor






Chapter 1: Introduction

Yodl stands for `Your Own Document Language' (originally: Yet Oneother
Document Language) and is basically a 
pre-processor to convert document files in a special macro language (the Yodl 
language) to any output format. The Yodl language is not a `final' language, 
in the sense that it can be viewed or printed directly. Rather, a document in 
the Yodl language is a `pre-document', that is converted with some macro 
package to an output format, to be further processed.

Yodl was designed in 1996 by Karel Kubat when he needed a good document
preprocessor to convert output to either LaTeX (for printing) or to
HTML  for publishing
via a WWW site. Although SGML does this too, he wanted something that is used
`intuitively' and with greater ease. This is reflected in the syntax of the
Yodl language, in the available macros of the Yodl macro package, and very
probably also in other aspects of Yodl. However, Yodl is designed to convert
to any output format; so it is possible to write a macro package that
converts Yodl documents to, say, the man format for manual pages. 

Some highlights of Yodl:
    
    o  Yodl allows the inclusion of files. This makes it easier to split up
a document into `logical' parts, each kept in a separate file. Thus, a `main
document' file can include all the sub-parts. (Imagine that you're the editor
of a journal. Authors are likely to send in their submissions in separate
files; inclusion can then be very handy!)
    o  Files which are included are searched for either `as-is', or in a
given `system-wide include' directory, similar to the workings of the C
preprocessor. Therefore, it is possible to create a set of include files
holding macros, and to place them into one macro directory. (See also chapter
4, where a macro package that is distributed with Yodl is
described.)
    o  For all the handled files (either stated on the commandline or
included), Yodl supplies an extension if none is present. The default
extension is .yo, but can be defined to anything in the compilation of the
Yodl program.
    o  Yodl supports conditional parsing of its input, controlled by defined
symbols. This resembles the #ifdef / #else / #endif preprocessor
macros of the C language. Yodl also supports other if clauses, e.g.,
to test for the presence of an argument to a macro.
    o  Yodl offers hooks to define counters, to modify them, and to use them
in a document. Thereby Yodl offers the possibility for automatic numbering of
e.g., sections. Of course, some document languages (e.g., LaTeX) offer this
too; but some don't. When converting a Yodl document to, say, HTML, this
feature is very handy.
    o  Yodl is designed to be easy to use: Yodl uses `normal' characters to
identify commands in the text, instead of insisting weird-looking tags or
escape characters.  Editing a document in the Yodl macro language is designed
to be as easy as possible.
    o  Similar to other document languages, Yodl supports `character
conversion tables' which define how a character should appear in the output.

This document first describes Yodl from the point of the user: how can
macros be defined, how is the program used etc.. Next, my own macro package is
presented and the macros therein described. Finally, this document holds
technical information about the installation and the inner workings of Yodl.


1.1: What's new since version 4.00.00?

    In Yodl Version 4.02.00 several new features were introduced.


    o  Three new builtin commands were implemented:
        
        o STRLEN returns the length of its argument, or the length of a
            symbol's text if the symbol's name is passed as argument to
            STRLEN. 
        o SUBSTR returns a substring of a specified length, starting at a
            specified offset of its first argument (or returns a substring
            of a symbol's text if the symbol's name is passed as argument to
            SUBSTR).

o  End-of-line comment is now available as the triplet
        \//. Following \// all subsequent characters on its
        line as well as initial blanks on the next line are skipped.

o  Redesigned yodlverbinsert, which now also concatenates multiple
        identically marked sections.

o  Added the   macro, writing a non-breaking space character.

o  Added the macro `tbl' (and support macros `tr, tc, tnc, ta,
        tnac' and `tline') as alternative to `table' (and support
        macros). The `tbl' macro extends `table', and simplifies
        defining tables.

In Yodl Version 4.00.00 some old features were removed, and several new ones
were introducted.


    o  The following builtin commands, considered obsolete since Yodl
        2.00.00, were removed:
        
        o DUMMY no replacement.
        o ENDDEF DECWSLEVEL should be used;
        o INCLUDELIT NOEXPANDINCLUDE should be used;
        o NEWCOUNTER DEFINECOUNTER should be used;
        o STARTDEF INCWSLEVEL should be used;
        o UNDEFINEMACRO DELETEMACRO should be used;
        o WRITEOUT FPUTS should be used;

o  Three new builtin commands were implemented:
        
        o PUSHSUBST allows temporary suppression (or activation) of
            SUBST definitions;
        o POPSUBS restores the activation type of SUBST definitions
        that was active just before the last PUSHSUBST call;
        o XXSUBST internally used builtin command.

o  The verb macro now starts with PUSHSUBST(0) and ends with
        POPSUBST().

o  The following macros, considered obsolete since Yodl
        2.00.00, were removed:
        
        endcenter
        enddit
        endeit
        endit
        endmenu
        endtable
        itemize
        menu
        mit
        node
        startcenter
        startdit
        starteit
        startit
        startmenu
        starttable
        


1.2: Why use Yodl?

    Yodl is not a word processor, not even an editor. At first glance you might
say, yeah, why should I learn Your Own Document Language? The answer is
exactly that: because it can be Your own document language!

First of all, Yodl may lower the threshold of new users to start writing
documents. An example of an excellent, though not very user-friendly document
language is LaTeX. Typing all the backslash and curly brace characters in
LaTeX and remembering that an asterisk must be typed as $*$ may be hard
at first. In such situations, a properly configured Yodl macro set removes
these obstacles and thereby helps novices. Yodl is designed to be easy to
learn.  As the Yodl package is growing, so is the manual. The ease of
`learning Yodl' may thus somewhat diminish, but just keep in mind: as long as
you need just plain texts, Yodl does OK. If you want more functionality, e.g.,
the composition of manual pages for Unix, dig into the documentation.

Second, Yodl permits to create more than one macro set, defining the same
commands, but leading to different output actions. Thereby, the same input 
file can be converted to several output formats, depending on the loaded macro 
set. In this, Yodl is a `general front' document language, which converts a 
Yodl document to a specialized language for further processing. This was of 
course one of my reasons to write Yodl: I needed a good converter for either 
LaTeX or HTML. 

Third, Yodl always allows an `escape route' to the output format. Most
situations can be handled with Yodl macros, but sure enough, some users will
want special actions for a given output format.  A typical example for the
necessity of such an escape route is the typesetting of mathematical formulas.
Say you want to use Yodl for a document that is converted either to LaTeX
(being a very good mathematical typesetter) or to HTML (a very poor
mathematical typesetter). An approach might be to decide inside the
document how to typeset a mathematical formula. Yodl provides conditional
command processing to accomplish this. The decision would be based on the
output format: for LaTeX, you'd typeset the formula using all the facilities
that LaTeX offers, and for HTML you'd use poor-mans typesetting. Typically,
other pre-processors for documents don't allow such escape routes. Well, Yodl
does.


1.3: Copying Yodl

    Yodl is free software; it is distributed under the terms of the 
GNU General Public Licence.  For details, please refer to the file
COPYING.


Chapter 2: Yodl User Guide

This section describes the yodl program from the point of a meta-user, 
one who is interested in how macro files work, or one who wants to write a new 
converter. If you're just interested in using Yodl with the pre-existing 
converters and macro files, skip this chapter and continue with the macro 
package description (chapter 4).

The Yodl program the main converter of the Yodl package. The basic usage 
of the yodl program, yodl's built-in macros, and the syntax of the
Yodl language is described here.


2.1: Using the yodl program

    Yodl reads one or more input files, interprets the commands therein, and
writes one output file. The program is started as:
    

    yodl options inputfile [inputfile...]
    

    In this specification, the options are optional. Most options have `long
variants' also, which are mentioned in the following list. In this list,
-x, --optionname are two alternate ways to specify option x. If -x
takes an argument, it may be specified immediately following the -x, but
separating blanks may also be used. Options not taking arguments can be
combined (e.g., -a -b -c may be combined to -abc). Arguments specified
with long options should be separated from the long option using a =
character.

The following options are currently available:


    o  -D, --define=NAME[=VALUE]: Defines name as a symbol. This
option is acts like DEFINESYMBOL(NAME)(). If =VALUE is added, NAME
is initialized to VALUE (identically to DEFINESYMBOL(NAME)(VALUE)).
    o  -d, --definemacro=NAME=EXPANSION: Defines NAME as macro
expanding to EXPANSION
    o  -h, --help: usage information is written to the standard error
stream, describing all of Yodl's options.
    o  -i, --index[=file]: `file' is the name of the index file. By
default <outputbase>.idx is used. No default when output is written to
stdout. The index file is processed by Yodl's post-processor, yodlpost.
    o  -I, --include=DIR: This defines the system-wide include directory
where Yodl searches for its input files. E.g. a statement to include a
given file, like:
        INCLUDEFILE(latex)
    Yodl now searches for the file latex in the current directory,
and when that fails, in the system-wide include directory. The system-wide
include directory is typically the place where the maintainer of a system
stores macro-files for Yodl. This searching process applies to files that are
included inside a document but also applies to filenames on the command line
when invoking the Yodl program.

The name of the included file (latex in the above example) is the bare
name, Yodl supplies a default extension (.yo), if necessary. 

The -I option overrules Yodl's built-in name for the system-wide
include directory. The built-in name is defined when compiling Yodl, and is,
e.g., /usr/share/yodl. Furthermore, the definition may contain $HOME,
which is replaced by the user's home directory if the `home' or `HOME'
environment variable is defined. It may also contain $STD_INCLUDE, which 
is replaced by the compilation defined standard include path. The standard
includepath may be overruled by either (in that order) the command line switch
-I or the tt(Yodl)_INCLUDE_PATH environment variable. By default, the
current directory is added to the standard include path. Hewver, when -I
or tt(Yodl)_INCLUDE_PATH is used, the current directory must be mentioned
explicitly.  The individual directories need not be terminated by a
/-character.  In distributed .deb archives, the standard directory is
defined as /usr/share/yodl (prefixed by the current working directory).
   o  -k, --keep-ws: Since Yodl version 2.00 blanks at the begin and end
of lines are ignored, even without a trailing \, when the `white space level'
is non-zero. Earlier versions kept these blanks. The legacy handling of white
space at end of lines can by obtained using the -k flag. Note that white
space are always kept when using verbatim copying, and when the white-space
level is zero.
    o  -m, --messages=SET: Set the so-called `message level' 
to a combination of the SET acdeinw. The letters of this set have the
following meanings:
    
    o  a: alert. When an alert-error occurs, Yodl terminates. Here Yodl
requests something of the system (like a get_cwd()), but the system fails.
    o  c: critical. When a critical error occurs, Yodl terminates.  The
message itself can be suppressed, but exiting can't. A critical condition is,
e.g., the omission of an open parenthesis at a location where a parenthesized
argument should appear, or a non-existing file in an INCLUDEFILE
specification (as this file should be parsed). A non-existing file with a
NOEXPANDINCLUDE specification is a plain (non-critical) error.
    o  d: debug. Probably too much info, like getting information about 
each character that was read by Yodl.
    o  e: error. An error (like doubly defined symbols). Once an error
has been encountered the remainder of the input is still parsed (up to a
maximum number of errors), but no output is generated.
    o  i: info. Not as detailed as `debug', but still very much info,
like information about media switches.
    o  n: notice. Information about, e.g., calls to the builtin
function calls.
    o  w: warning. Something you should know about, but probably not
affecting Yodl's proper functioning

Non-configurable is the handling of an emergency message. These
messages can't be suppressed, but shouldn't happen, as they point to some
internal error. It would be appreciated to 
        receive information 
    about these messages if they ever occur.
    o  -n, --max-nested-files=NR: This option causes Yodl to abort when
the number of nested input files exceeds NR, which is 20 by
default. Exceeding this number usually means a circular definition somewhere
in the document. This is the case when, a file a.yo includes b.yo,
while b.yo includes a.yo etc.. It does not prevent recursive macro- or
subst-replacements. For that the -r (--max-replacements) option is
available.
    o  -o, --output=FILE: This option causes Yodl to write its output to
FILE. By default, the output goes to the standard output stream. E.g.,
you can use Yodl to read a file input and to write to
output with the following two commands:
    
        yodl input > output
        yodl -ooutput input
    
    The difference being that in the latter case an index file is generated,
but not in the former case. Notice that writing an index file can be forced
when the --index option is specified.
    o  -p, --preload=CMD: This option `pre-loads' the string cmd. It
acts as though cmd was the first command in the first input file that is
processed by Yodl.

More than one --preload=CMD options may be present on the command
line.  Each of the commands is then processed in turn, before reading 
any file.
    o  -r, --max-replacements=NR: This option causes Yodl to abort when
the number of macro calls or subst-replacements exceeds NR * 10,000. 
By default, NR equals 1. Setting --max-replacements=0 implies that 
no macro- or subst-replacement checks are performed.
    o  -t, --trace: This option enables tracing: while parsing, Yodl
writes its output to the standard error stream. As is the case with the -k
option, this option is defined for debugging purposes only.
    o  -V, --version. This option shows Yodl's actual version.
    o  -v, --verbose: This option increases Yodl's `verbosity level' and
may occur more than once. By default yodl shows alerting, critical,
emergency and error messages. Each --verbose option adds a next
message level. In order, warning, notice, info and debug messages are
added to this set. It is also possible to suppress messages. The
VERBOSITY builtin can be used for that.
    o  -W, --warranty. This option shows a warranty disclaimer and a
copyright notice. 
    o  -w, --warn: The presence of this option caused Yodl to warn when,
e.g., symbols are redefined.

The inputfile elements on the command line specify which files Yodl should
process. All names are supplied with an extension\ (this extension is
defined in the installation of Yodl and is usually .yo). The files are then
searched for in the directories mentioned in the include-path. Files may also
be specified using absolute pathnames.

Note that all filenames on the command line are input files. To define an
output file, either use the --output option or redirect the output. 


2.2: The Yodl grammar

    The grammar which is used by Yodl mixes `real' text that should appear on the
output with markups: commands for Yodl. The markups must follow a certain
grammar, which is described in this section. Yodl therefore falls in the
category of `markup languages', in contrast to `WYSIWYG'-programs. As a
consequence, Yodl promotes concept-oriented writing.

Basically, Yodl only does `something special' when it encounters the name of a
builtin function or the name of a user-defined macro, followed by a
parenthesized argument. Sometimes a function or macro requires multiple
arguments, which must then be specified in sequence.  All required parameter
lists, however, must be specified within the same input file. It is not
allowed to split the activation of a builtin function or macro over multiple
input files. Plain text, on the other hand, may be split over multiple files.

In this section the elements of Yodl's grammar are briefly discussed.


2.2.1: Language elements

        At the lowest level, Yodl's lexical scanner returns small pieces of
information to its parser. These pieces of information are called tokens,
and consist of elements like a blank space, a non-blank character, or an
end-of-ile flag. These tokens are at too small an aggregation level to be
useful for the current user-guide, so here we concentrate our discussion 
on the next aggregation level: compound elements and conceptual elements. 

Compound elements relate to the basic tokens as words in a sentence to the
individual letters of the words. These compound elements are identifiers,
names, numbers, parameter lists and arguments.

Conceptual elements are found at the next higher aggregation levels:
builtin functions are the buildin blocks for all of Yodl's functionality,
symbols and counters are Yodl's variables, and (user defined)
macros extend Yodl's functionality beyond those of the basic builtin
functions.

In the coming sections these basic and conceptual elements are discussed in
greater detail.


2.2.1.1: Identifiers and Names

            Identifiers are names that can have a special meaning in the Yodl
language. E.g., the sequence INCLUDEFILE is an identifier: when
followed by a filename in parentheses, Yodl will take some special action (in
this case, read the file as a Yodl-source file).

Identifiers may consist of uppercase or lowercase characters. No other
characters may appear in them. 

In particular, note that this diverts from the well known definition for
identifiers used in most programming languages: identifiers may not contain
underscores, nor digits. Yodl, therefore, won't accept identifiers like
run4 or under_score.

Names are sequences of characters, not containing white space characters.
(i.e., any series of characters not containing spaces, tabs or
newlines). Names are allowed with certain builtin functions, like the
INCLUDEFILE function, expecting the name of a file as its argument.


2.2.1.2: Numbers

            Numbers consist of digits and an optional minus sign. They are most
often used for so-called counters. In some contexts (e.g. with the builtin
function VERBOSITY [VERBOSITY], hexadecimal
numbers are allowed. Hexadecimal numbers have 16 `digits': the familiar 0-9,
but also a-f (or A-F), representing the decimal values 10 until 15,
respectively. Hexadecimal values are usually prefixed by 0x, for example
0x4e.  

In other contexts (in particular, with character tables [CHARTABLES]),
octal numbers or character constants are allowed too.

An octal number only consists of the digits 0-7. In Yodl, octal values
must consist of three digits, and must be preceded by a backslash.

Character constants may very well be considered numerical values. Character
constants consist of a character value between single quotes, for example
'a'. 

Refer to section 2.3 for more detailed information about the use
of octal values and character constants.

Yodl has no concept of floating point values nor does it have facilities for 
performing floating point arithmetic.


2.2.1.3: Arguments to builtin functions and macros

            Arguments that are passed to Yodl builtin functions or user-defined macros
must be surrounded by a pair of matching open- and close-parentheses.  Each
parameter list contains exactly one argument.

An argument is recognized when it immediately follows the name of a builtin
function or user-defined macro. Some functions or macros expect multiple
arguments. In those cases, the required number of arguments must be provided,
possibly separated from each other by white-space.

For example, the following shows how to call the builtin function
DEFINECOUNTER, expecting two arguments:
        
    DEFINECOUNTER(MyCounter)()
    DEFINECOUNTER(MyCounter)    ()
    DEFINECOUNTER(MyCounter)(12)
        

Yodl recognizes the arguments of macros when delimited by ( and
) characters. As long as the numbers of opening and closing
parentheses match, Yodl correctly recognizes the list. E.g., given a
hypothetical macro somemacro, the following code sample shows the macro
followed by one argument:
        
    somemacro(Here is a chunk of text.)
    somemacro(Here is a some (more) text.)
         
    An error occurs when the parentheses aren't balanced: i.e., when the
argument consists of more opening than closing parentheses or vice versa
To handle such situations, Yodl offers a `literal-character' mechanism (see
the CHAR macro in 3.1.4) and a `global substitution' mechanism (see
the SUBST macro in 3.1.62). For example, to send the text
        here's a ")" closing parenthesis 
    as an argument to our hypothetical macro somemacro, the following can
be used:
        
    COMMENT(-- Alternative 1: using CHAR --)
    somemacro(here's a "CHAR(41)" closing parenthesis)

    COMMENT(-- Alternative 2: using SUBST --)
    SUBST(closepar)(CHAR(41))
    somemacro(here's a "closepar" closing parenthesis)
        
    Both methods have disadvantages: the CHAR method requires you to
remember that an ASCII 41 is a closing parenthesis. The SUBST method
defines a string closepar that is always expanded to a closing
parenthesis, wherever it may occur in the text. But whatever method is used,
it should be clear by now that unbalanced arguments can be handled by
Yodl. Also, remember that unbalanced parenthesis pairs are only relevant in
argument lists. Yodl handles parentheses in normal text as ordinary
characters.


2.2.1.4: Builtin functions

            The building blocks of Yodl's functionality are its builtin
functions. Builtin functions exists to manipulate all of Yodl's builtin types
(character tables, counters, macros and symbols) and to do basic bookkeeping
and flow-control: it is possible to test values of counters and symbols, to
include other input files, to generate warning and error messages, and to
start child- or subprocesses. Each builtin function is described in a separate
subsection of section BUILTIN [BUILTIN].


2.2.1.5: Character translation tables

            Character translation tables exist to perform conversion specific
transformations. For example, in html, the \'e is written as
é, but in LaTeX it's written as \'e. Rather than
using a potentially long if-else ladder to determine how to set a particular
character, a character translation table can be used. The character
translation table of a particular conversion is then activated only for that
type of conversion. 

Character table translations are used very late during the processing of
Yodl's input s: it is the output generator that handles the character
translations. Consequently, macros or builtin function calls that might appear
in a character's redefinition element of a character table are not
expanded. In practice this never is a point of concern. In section
2.3 the use of character translation tables is discussed in
detail.


2.2.1.6: Counters

            Some document languages (notably LaTeX) automatically prefix numbers when
typesetting sections, subsections, tables, figures etc..  Other document
languages (e.g. html) don't. 

Therefore, a macro package that converts a Yodl document to LaTeX doesn't need
to provide the numbering of sections etc.. However, if you do want the
numbering and if you want to convert documents to, say, html, then you
must take care of the numbering yourself.

Counters exist to make this possible. Counters can be incremented, can be
given a particular value, can be given a new value temporarily and can be
removed. They always contain integral values, which may be negative.

Section 2.5 describes the use of counters in more detail.


2.2.1.7: Macros

            Macros are comparable to builtin functions, but they can be defined in Yodl
input files. Macros add functionality to Yodl exceeding the basic
functionality of the builtin functions. Macros can have arguments, and they
are used in exactly the same way as builtin functions are used.

When Yodl encounters a macro, it acts as follows:
    
    o  Its arguments are obtained, by reading its argument lists. These 
arguments are not interpreted in any way. They are simply removed from the
input, and stored for further processing;
    o  References to arguments in the macro's definition (using the ARG#
notation, where # is the sequence number of a particular argument) are
replaced by the literal text of the corresponding macro's arguments.
    o  The thus modified definition text is now pushed back into the input
stream, to be processed by Yodl's lexical scanner.

Defining macros is described in section 3.1.11. Macros may be
defined, deleted, renamed, and temporarily given other definitions.


2.2.1.8: Nousermacros

            When Yodl is started using the -w flag on the command line, then warnings
are generated when Yodl encounters a possible macro name, followed by a
parenthesized argument, without finding a macro by that name.  Yodl then
prints something like cannot expand possible user macro.

Examples of such sequences are, The necessary file(s) are here, or see
the manual page for sed(1). The candidate macros are file and sed, as
these names could very well have been `valid' user macros followed by their
arguments.

A nousermacro can be defined to suppress these warnings, by informing Yodl
that file and sed aren't macros. Nousermacros may be defined and
undefined. See sections 3.1.41 and 3.1.16 for
details). 


2.2.1.9: Symbols

            Yodl symbols contain text. They were introduced to allow the flexible
expansion of text, the length and/or content of which cannot be determined in
advance. In particular, symbols are useful to store a series of LaTeX document
options, or a series of html body options. In earlier versions of Yodl
complex and confusing constructions using nested definitions of macros were
used for this. These macros were not only confusingly complex, but they also
suffered from a hard-coded maximum. Symbols solve these drawbacks, and now
that they are available, they are used for all natural situations in which an
initially unknown piece of text must be stored. National language specific
strings are another useful area in which symbols can be used. The symbol
CONTENTSHEADING can be set to the name of the contents heading (e.g.,
Contents in English, Inhoud in Dutch, Contenido in Spanish, and
macros can simply insert the value of the symbol CONTENTSHEADING at the
appropriate location. 

Symbols can be defined [DEFINESYMBOL], removed [DELETESYMBOL],
(temporarily [PUSHSYMBOL] or permanently [SETSYMBOL]) be given
another value; pushed symbol values can be restored [POPSYMBOL] at a
later point. Of course, their values can also be inserted [SYMBOLVALUE]
into Yodl's output file.


2.2.2: Line continuation

        To make the typing of input easier, Yodl allows you to end a line with a
backslash character \ and to continue it on the next line. That way you can
split long lines to fit your screen. When processing its input, Yodl treats
these lines as one long line, and ignores the final \ character. This
feature only works when the \ character is the last one on the line (only a
physical newline may follow).

When the line following the one with the \ character has leading spaces,
then these are omitted. This allows you to `indent' a file as you wish, while
the space characters of the indentation are ignored by the Yodl program. 

A trivial example is the following:
    
    Grandpa and\ 
    grandma are sitting on the sofa.
        
    Due to the occurrence of the \ character in the sequence and\, Yodl
combines the lines to
        
    Grandpa andgrandma are sitting on the sofa.
        
    Note that the spaces before grandma are ignored, since this is the
second line following a \ character.

If you do want one or more spaces while joining lines with \, put the
spaces before the \ character.
    

    Summarizing:
    
    o  A Line ending in a backslash character is merged with the next
line. 
    o  This only happens if the \ character is the last character of the 
line, no spaces may appear behind the \.
    o  When merging lines, Yodl ignores leading spaces of the second line.

The question is of course, how do you accomplish that a line really ends
with a \, when you do not want Yodl to merge it with the following line?
In such a case, type a space character following your \: Yodl won't combine
the lines.  Or set the \ character as CHAR(\) or CHAR(92)
(see section 3.1.4 for the CHAR macro).

When Yodl processes input files, and the white-space level exceeds zero
(see section 3.1.35), then all lines are processed as if they
terminated by a \. This behavior was implemented first with Yodl version
2.00. It can be suppressed using Yodl's -k flag.


2.2.3: The +identifier sequence

        There may be situations in which you must type a macro name right after a
sequence of characters, while Yodl should recognize this. Imagine that someone
wrote a great macro footnote for you\ (someone did, in fact, see
the next chapter), to typeset footnotes. If you'd type in a document:

The C Programming Languagefootnote(as defined by 
Kernighan and Ritchie) ...

then of course Yodl would fail to see the start of a macro in the sequence
Languagefootnote. You could say

The C Programming Language footnote(as defined by 
Kernighan and Ritchie) ...

but that would introduce a space between Language and the footnote.
Probably you don't want that, since spaces between a word and a footnote
number look awful and because of the fact that the footnote number might be
typeset on the following line.

For these special situations, Yodl recognizes the +identifier sequence as
the start of a macro, while the + sign is effectively ignored. In the
above example you could therefore use

The C Programming Language+footnote(as defined by 
Kernighan and Ritchie) ...

The +identifier recognition only works when the identifier following the
+ sign is a macro. In all other situations, a + is just a plus-sign.

(The +identifier sequence furthermore plays an important role in macro
packages. If you're interested, see the file shared.yo which is by default
installed to /usr/local/lib/yodl.)


2.2.4: Preventing macros from being expanded

        One more feature of the Yodl language remains to be described. In the previous
section it was described how a macro may be called immediately following
alphabetical characters. What about the opposite situation where we do not
want a macro to be expanded in a particular situation? The NOUSERMACRO
builtin command (cf. section 3.1.41) may be used to suppress the
interpretation of a character sequence (e.g., file(...)) as a macro, but
what if a macro should not be expanded in the occasional situation? For this
case various solutions are available:
    
    o  First, the tt(...) and verb(...) macros may be used to
suppress macro expansion. These macros also temporarily alter the
typesetting font, though.
    o  Second, NOEXPAND() builtin command may be used: the macro name
may be passed to NOEXPAND(), immediately followed by the `argument list':
        Like this: NOEXPAND(NOEXPAND)(hello world)
    o  Third, the nop() macro may be used to separate a macro name from
its argument list:
        Like this: NOEXPAND+nop()(hello world)


2.3: Character tables

    The Yodl language provides a way to define character translation tables, to
activate them, and to deactivate them. A character translation table defines
how a character in the input will appear in the output.

There are two main reasons for the need of character translation tables.
First, a document language becomes much easier to use when you can type an
asterisk as * instead of $*$ or \verb/*/ (these are sequences from the
LaTeX document language). Hence, a mechanism that expands a * in the input to
to \verb/*/ on the output, saves the users a lot of typing.

Second, forcing users to type weird sequences won't work if you're planning on
converting the same Yodl document to a different output format. If the user
types \verb/*/ in the input to typeset an asterisk in the output, how
should he or she arrive at a single * in the output in another output format? 

The solution is of course to define the translation for an input character
like * given the output format.


2.3.1: Defining character tables

        
The built-in macro DEFINECHARTABLE defines a character translation table.
It takes two arguments: the name of the table and the character
translations. Hence, each table is defined by its own name.

As an example of a table, consider the following fragment.  It defines a table
that translates the upper case characters A to E to their lower case
equivalents:

DEFINECHARTABLE(tolower)(
    'A' = "a"
    'B' = "b"
    'C' = "c"
    'D' = "d"
    'E' = "e"
)

Each DEFINECHARTABLE statement must have a non-empty second
parameter. "Empty" character tables cannot be defined, though one
non-translation table is built-in.

The syntaxis of the second argument is as follows:

o  On separate lines, input characters are mapped to a sequence to
    appear on the output.

o  Per line, the input character is specified as 'c', c being
    any character. Escape-sequences from the C programming language can be
    used in this specification; Yodl supports the sequences \a (alert),
    \b (beep), \f (formfeed), \n (newline), \r (carriage
    return), \t (tab), and \v (vertical tab). Octal and hexadecimal
    constants may also be used. E.g., character Y may also be specified
    using the octal value \131 or the hexadecimal value \x59. Any
    other character following a \ defines itself: \\ represents a single
    backslash character.

o  Following the character specification, a = must appear.

o  Following that, a sequence of one or more characters appears,
    enclosed in double quotes, defining the translation. Again, escape
    sequences can be used, as in:

'\n' = "End of line\n"

Such a mapping adds the text End of line to each line, since each
    newline character in the input is replaced by the text End of line,
    followed by the newline itself.

Starting with Yodl 2.14.0 octal and hexadecimal constants may also be used
    within the double quoted string. E.g., character Y may also be
    specified using the octal value \131 or the hexadecimal value
    \x59.  As an example where the octal/hexadecimal values may be useful
    consider the processing of a man-page. The character representations for
    the literal double quote (") in troff is
    \(dq\&. However, since ( cannot be written literally
    in the character translation table since that would result in unbalanced
    parentheses while processing the character table's definition. Also,
    CHAR(40) cannot be used, since character table conversiond are
    performed by the output generator, which is called after the macro
    expansions have been performed. This it would result in the literal text
    CHAR((40)) appearing in the manual page.

Using the octal character representation in the chartable specification
    for the " character appearing in man-page the problem can now be
    solved. The actual specification used is:  '"' = "\\\050dq\\&" 

Translations which are not specified in the table are left to the default,
which is to output the character as-is.

Note that the character table translation is something that the yodl
program does as one of its last actions, just before sending text to the
output file. The expansion text is not further processed by yodl, except
for the conversion of C-type escape sequences to ordinary characters. The
expansion text should therefore not be protected by, e.g., NOTRANS
(unless of course you want some character to generate the text NOTRANS
on the output).


2.3.2: Using character tables

        
A defined translation table is activated by the macro USECHARTABLE. This
macro takes one argument, which may be:


    o  empty, in which case the default mapping is restored,
    o  a name of a previously defined character table.

The default mapping, selected when an empty argument is given, means that Yodl
enters its `zero translation state', meaning no character translation at all.


2.3.3: Pushing and popping character tables

        Besides the previously described macro USECHARTABLE(), Yodl has one other
mechanism of activating and deactivating character translation tables. This
mechanism uses a stack, and hence, the related macros are appropriately named
PUSHCHARTABLE() and POPCHARTABLE().

o  PUSHCHARTABLE(name) pushes the currently active translation
    table onto a stack, and activates the table identified by name. The
    argument may be empty; in that case, the zero-translation table is
    activated (analogously to USECHARTABLE()).

o  POPCHARTABLE() activates the translation table that was last
    pushed. There is no argument to this macro.

Using the push/pop mechanism is handy when a table must be temporarily
activated, but when it is not known which table exactly is active prior to the
temporary activation. E.g., imagine that you need to use a character table
called listing to typeset a listing, but that you do not know the current
table. The pushing and popping mechanism is then used as follows:

COMMENT(First, we save the current table on the stack and
        we activate our "listing" table.)
PUSHCHARTABLE(listing)

COMMENT(Now the text is question is typeset.)
...

COMMENT(The previously active table is re-activated, whatever its name.)
POPCHARTABLE()


2.4: Sending literal text to the output

    The Yodl program has several built-in macros that can be used to send literal
text to the output file. The macros are listed in the chapter 3.1 and
are briefly described here:
    
    o  CHAR takes one argument: the ASCII number of a 
character or the character itself. The character is sent to the output 
file without being translated with the currently active character 
translation table.
    o  NOTRANS takes one argument: the text in question. The 
text is neither parsed (i.e., macros in it are not expanded), nor 
translated with the current character translation table.
    
    
The NOTRANS macro is conceptually like a series of CHAR macros.
    o  NOEXPAND takes one argument: the text in question. The 
text is not parsed, but it is translated with the current character 
translation table.
    o  POPSUBST takes no argument, and restores the SUBST
interpretation status that was active just before the most recently called
PUSHSUBST builtin macro call.
    o  PUSHSUBST takes one argument: 0 or a non-zero value (commonly
1). Following PUSHSUBSTS(0) SUBST-definitions are ignored; following
PUSHSUBSTS(1) SUBST-definitions are used.

To illustrate the need for the distinction between NOTRANS and 
NOEXPAND, consider the following. The HTML converter (described in  
chapter 4) must be able to send HTML commands to the output 
file, but must also be able to send literal text (e.g., a source file 
listing). The HTML commands of course must be neither translated with any 
character table, nor must they be expanded in regard to macros. In contrast, a 
source file listing must be subject to character translations: the &, 
< and > characters can cause difficulties. Two possible macros for a 
HTML converter are:
        
    COMMENT(--- htmlcommand(cmd) sends its argument as a HTML command 
                to the output ---)
    DEFINEMACRO(htmlcommand)(1)(NOTRANS(ARG1))
        
    COMMENT(--- verb(listing) sends the listing to the output ---)
    DEFINECHARTABLE(list)(
        '&'     =   "&amp;"
        '<'     =   "&lt;"
        '>'     =   "&gt;"
    )
    
    DEFINEMACRO(verb)(1)(
        USECHARTABLE(list)
        NOTRANS(<listing>)
        NOEXPAND(ARG1)
        NOTRANS(</listing>)
        USECHARTABLE(standard)
    )
        
    In this example it is assumed that a character translation table
standard exists, defining the `normal' translations. This table is
re-activated in the verb macro.

The currently defined verb macro for, e.g., html conversion looks like
this:
    
    DEFINEMACRO(verb)(1)(
        PUSHSUBST(0)
        NOTRANS(<pre>)
        XXnl()
        NOEXPAND(ARG1)
        XXnl()
        NOTRANS(</pre>)
        XXnl()
        POPSUBST()
    )
    
    Here, the surrounding PUSHSUBST(0) and POPSUBST() pair prevent the
interpretation of multi-char SUBST definitions like 
        
    SUBST(\"e)(+NOTRANS(&euml;))
        
    inside verb environments, causing unexpected translations in pieces of
code like
        
    cout << "\"evil\" code\n";
        
    which, if the PUSHSUBST command isn't used,  is converted to 
        
    cout << "&eacute;vil\" code\n";
        


2.5: Counters

        Some document languages (notably LaTeX) automatically prefix numbers when
typesetting sections, subsections, tables, figures etc..  Other document
languages (e.g. HTML) unfortunately don't.

Therefore, a macro package that converts a Yodl document to LaTeX doesn't
need to provide the numbering of sections etc.. However, if you do want the
numbering and if you want to convert documents to, say, HTML, then you must
take care of the numbering yourself.

This section describes the counters in Yodl: how to create counters,
how to use them, etc..


2.5.1: Creating counters

        Before a counter can be used, it must be created using DEFINECOUNTER or
PUSHCOUNTER. These functions expects two arguments: the name of the
counter and an (optional) integral additive expression. When provided, the
expression may contain binary + and unary or binary - operators; its operands
may be integral values or the names of existing counters. Additive expressions
may not contain white space characters. If an additive expression is provided
it is evaluated and its value is then used to initialize the named counter. If
the second argument is empty then the counter is initialized to zero (0).

For example, let's say that our macro package should provide two
sectioning commands: section and subsection. The sections should be
numbered 0, 1, 2, etc., and the subsections 1.1, 1.2, 1.3 etc.. For this we
can define two counters:
        
    DEFINECOUNTER(sectcounter)()\//       initialized to 0
    DEFINECOUNTER(subsectcounter)(1)\//   initialized to 1
    


2.5.2: Using counters

        The builtin function  COUNTERVALUE(somecounter) expands to the value of
somecounter. E.g., if the current value is 2, then the value 2 is inserted
into the output object. It is an error to use COUNTERVALUE on a
non-existing counter or on a counter not having a defined value (see below).

Yodl has several functions to modify and/or to set the values of counters. The
counter's value, named expression below, is an additive expression: it may
contain binary + and unary or binary - operators. The operands may be integral
values of the names of existing counters. Additive expressions may not
contain blank spaces.

The functions modifying values of counters are:    
    
    o  POPCOUNTER(somecounter): This function pops the most recently
pushed value off the counter's stack, assigning it to somecounter. An
error occurs when somecounter doesn't exist. If the counter was never
pushed, it still exists following POPCOUNTER, but its value is
undefined: using COUNTERVALUE(somecounter) in that case generates an
error. 

o  PUSHCOUNTER(somecounter)(expression): This function pushes the
current value of the counter somecounter on the counter's stack, making
expression's value its new value. Its second argument may be empty in
which case the counter is initialized to 0. When somecounter doesn't yet
exist, it is created with an initial value of expression.

o  SETCOUNTER(somecounter)(expression): This function sets the value
of somecounter to expression's value. The function does not expand to
anything; i.e., it does not write to the output file.

o  ADDTOCOUNTER(somecounter)(expression): This function adds
expression's value to somecounter.

o  USECOUNTER(somecounter): This function first increments
somecounter's value, and then writes the value of the counter to the
output file.

This function is particularly useful in combination with
DEFINECOUNTER: since DEFINECOUNTER initializes a counter to zero,
USECOUNTER can be used to increment the value and to output it. The first
time that USECOUNTER is used on a new counter, the value 1 appears on
the output file. The next time, expression 2 appears on the output file etc..

Given the numbering requirements of the hypothetical commands section and
subsection (see the previous section), we can now complete the
definitions:

DEFINECOUNTER(sectcounter)
DEFINECOUNTER(subsectcounter)

DEFINEMACRO(section)(1)(\ 
SETCOUNTER(subsectcounter)(0)\ 
USECOUNTER(sectcounter) ARG1)

DEFINEMACRO(subsection)(1)(\ 
COUNTERVALUE(sectcounter).USECOUNTER(subsectcounter) ARG1)


Chapter 3: All builtin functions


3.1: Yodl's builtin commands

As mentioned previously, Yodl's input consists of text and of commands.  Yodl
supports a number of built-in commands which may either be used in a Yodl
document, or which can be used to create a macro package.

Don't despair if you find that the description of this section is too
technical. Exactly for this reason, Yodl supports the macro packages to make
the life of a documentation writer easier. E.g., see chapter 4
that describes a macro package for Yodl. 

Most built-in functions and macros expand the information they receive the way
they receive the information. I.e., the information itself is only evaluated
by the time it is eventually inserted into an output medium (usually a
file). However, some builtin functions evaluate their argument(s)
once the argument is processed. They are:
    
    o  The ERROR built-in function (see section 3.1.18);
    o  The EVAL built-in function (see section 3.1.19);
    o  The FPUTS built-in function (see section 3.1.21);
    o  The INTERNALINDEX built-in function (see section
            3.1.36);
    o  The PUSHSUBST built-in function (see section 3.1.56);
    o  The TYPEOUT built-in function (see section 3.1.65);
    o  The UPPERCASE built-in function (see section 3.1.66);
    o  The WARNING built-in function (see section 3.1.70);
    o  The XXSUBST internal use only built-in function;

All other built-in functions will not evaluate their arguments. 
See the mentioned functions for details, and in particular EVAL() for a
description of this evaluation process.


3.1.1: ADDTOCOUNTER

    The ADDTOCOUNTER function adds a given value to a counter. It expects two
arguments: the counter name, and an additive expression defining the value to
add. The counter must be previously created with DEFINECOUNTER.

The additive expression may not contain blank spaces and may use + and -
operators, its operands may either be integral numeric values or names of
(defined) counters.  The resulting value can be negative; in that case, a
value is subtracted from the destination counter.

For example, if one and two are counters, then 
        
    ADDTOCOUNTER(one)(-two)\//    subtracts two's value from one
    ADDTOCOUNTER(one)(two+two)\// adds 2 x two's value to one
        

See further section 2.5.


3.1.2: ADDTOSYMBOL

    Since Yodl version 2.00 symbols can be manipulated. To add text to an existing
symbol the builtin ADDTOSYMBOL is available. It expects two parameter
lists: the symbol's name, and the text to add to the symbol.  The symbol must
have been created earlier using DEFINECOUNTER (see section
3.1.10). The macro's second argument is not evaluated while
ADDTOSYMBOL is processed. Therefore, it is easy to add the text of another
symbol or the expansion of a macro to a symbol value. E.g.,
        
    ADDTOSYMBOL(one)(SYMBOLVALUE(two)XXnl())
        
    This adds the text of symbol two, followed by a new line, to the
contents of symbol one only when symbol one is evaluated, not when 
ADDTOSYMBOL is evaluated.

Example:
        
    ADDTOSYMBOL(LOCATION)(this is appended to LOCATION)
        


3.1.3: ATEXIT

    ATEXIT expects one argument. The argument is appended to the output
file. Note that this text is subject to character table translations etc..

An example using this function is the following. A document in the
LaTeX typesetting language requires \end{document} to occur at the end of
the document. To automatically append this string to the output file, the
following specification can be used:
        
    ATEXIT(NOEXPAND(\end{document}))
        
    Several ATEXIT lists can be defined. They are appended to the output
file in the reverse order of specification; i.e., the first ATEXIT
list is appended to the output file last. That means that in general the
ATEXIT text should be specified when a `matching' starting command is sent
to the output file; as in:
        
    COMMENT(Start the LaTeX document.)
    NOEXPAND(\begin{document})
    
    COMMENT(Ensure its proper ending.)
    ATEXIT(NOEXPAND(\end{document}))
        


3.1.4: CHAR

    The command CHAR takes one argument, a number or a character, and outputs
its corresponding ASCII character to the final output file.  This command is
built for `emergency situations', where you need to typeset a character
despite the fact that it may be redefined in the current character table (for
a discussion of character tables, see 2.3). Also, the CHAR
function can be used to circumvent Yodl's requirement that open- and
close-parentheses must match.

The following arguments may be specified with CHAR (attempted in this
order):
    
    o  A decimal number indicating the number of the character in the
        ascii-table (for example CHAR(41));
    o  A plain, single character  (for example CHAR(#)).

So, when you're sure that you want to send a printable character that is
not a closing parenthesis to the output file, you can use the form
CHAR(c), c being the character (as in, CHAR(;)).
To send a non-printable character or a closing parenthesis to the output file,
look up the ASCII number of the character, and supply that number as argument
to the CHAR command.

Example: The following two statements send an A to the output file.
        
    CHAR(65)
    CHAR(A)
        
    The following statement sends a closing parenthesis:
        
    CHAR(41)
        
    Another way to send a string to the output file without expansion by
character tables or by macro interpretation, is by using the function NOTRANS
(see section 3.1.40). If you want to send a string to the output
without macro interpretation, but with character table translation,
use NOEXPAND (see section 3.1.37).


3.1.5: CHDIR

    The command CHDIR takes one argument, a directory to change to. This
command is implemented to simplify the working with includefile (see
includefile in yodlmacros(7)).  As a demonstration,
consider the following fragment:
        
    includefile(subdir/onefile)
    includefile(subdir/anotherfile)
    includefile(subdir/yetanotherfile)
        
    This fragment can be changed to:
        
    CHDIR(subdir)
    includefile(onefile)
    includefile(anotherfile)
    includefile(yetanotherfile)
    CHDIR(..)
        
    The current directory, as given to CHDIR, only affects how
includefile searches for its files. 

Note that this example assumes that the current working directory is a
member of Yodl's include-path specification (cf., Yodl's --include
option). 


3.1.6: COMMENT

    The COMMENT function defines one parameter list. The text that is passed
as argument is treated as comment. I.e., it is ignored; it is not copied to
the final output file.

As an alternative to (short) COMMENT the triplet \// can be
used. It starts `end of line' comment, ignoring all characters on a line
starting at \// up to the first non-blank character encountered on the
next line. If the next line's first non-blank characters are \//, then
that begins another end of line comment, which will therefore also be skipped.

To actually write
    \// or, using the current font: \//
in a yodl-converted document, write, e.g., 
    tt(\)tt(//) or, using the current font: nop(/)// 
in a yodl-source file, and write \CHAR(/)/ in verb sections.

Example:
        
    Hello world\// producess Hello world, skipping the rest
        \// this line is completely ignored
       s\// at this point Hello worlds has been produced.
        


3.1.7: COUNTERVALUE

    COUNTERVALUE's argument expands to the value of a counter. Its single
argument must contain the name of a counter.  The counter must have been
created earlier using the builtin DEFINECOUNTER.
    
   
    Example:
        
    The counter has value COUNTERVALUE(MYCOUNTER).
        
    See also section 2.5.


3.1.8: DECWSLEVEL

    DECWSLEVEL requires one (empty) argument. 
It reduces the current white-space level. The white-space level typically is
used in files that only define Yodl macros. When no output should be generated
while processing these files, the white-space level can be used to check for
this. If the white-space level exceeds zero, a warning is generated if
the file produces non-whitespace output. The builtin function DECWSLEVEL
is used to reduce the whitespace level following a previous call of
INCWSLEVEL. 

Once the white space level exceeds zero, no output will be
generated. White space, therefore effectively is ignored. The white space
level cannot be reduced to negative values. A warning is issued if that would
have happened if it were allowed.

Example:
        
    INCWSLEVEL()
    DEFINESYMBOL(....)
    DEFINEMACRO(...)(...)(...)
    DECWSLEVEL()
        
    Without the INCWSLEVEL and DECWSLEVEL, calls, 
the above definition would generate four empty lines to the output stream.

The INCWSLEVEL and DECWSLEVEL calls may be nested. The best
approach is to put an INCWSLEVEL at the first line of a macro-defining
Yodl-file, and a matching DECWSLEVEL call at the very last line.


3.1.9: DEFINECHARTABLE

    DEFINECHARTABLE is used to define a character translation table.
The function expects two parameterlists, containing the name of the 
character table and character table translations
on separate lines. These character table  translations are of the form 
        
    character = quoted-string
        
    Here, character is always a value within single quotes. It may be a single
character, an octal character value or a hexadecimal character value. The
single character may be prefixed by a \-character (e.g., '\\'). The octal
character value must start with a backslash, followed by three octal digits
(e.g., '\045'. The hexadecimal character value starts with 0x,
followed by two hexadecimal characters. E.g., '0xbe'. The double quoted
string may contain anything (but the string must be on one line), possibly
containing escape-sequences as well: in the double quoted string the standard
C escape sequences \a (alert), \b (beep), \f (formfeed),
\n (newline), \r (carriage return), \t (tab), and \v (vertical
tab) are recognized and automatically converted to their special
meanings. Starting with Yodl 2.14.0 octal and hexadecimal constants may also
be used. E.g., character Y may also be specified using the octal value
\131 or the hexadecimal value \x59. Any other character following a
backslash character (\) defines itself: \\ represents a single
backslash character.

Example:
        
    DEFINECHARTABLE(demotable)(
        '&'     = "&amp;"
        '\\'    = "\\backslash"
        '\045'  = "oct(45)"
        '0xa4'  = "hex(a4)"
    )
        
    The builtin function DEFINECHARTABLE does not activate the
table. The table is merely defined. To activate the character translation
table, use USECHARTABLE. The discussion of character tables is postponed
to section 2.3.


3.1.10: DEFINECOUNTER

    DEFINECOUNTER creates a new counter. This builtin function expects two
arguments: the name of the counter and an additive expression whose value is
used to initialize the counter.

The additive expression may not contain blank spaces and may use + and -
operators, its operands may either be integral numeric values or names of
(defined) counters.  The resulting value can be negative; in that case, a
value is subtracted from the destination counter.

Examples:
        
    DEFINECOUNTER(year)(1950)
    DEFINECOUNTER(nTimes)(year+12)\// initializes nTimes to 1962
        

See also section 2.5 and the USECOUNTER and ADDTOCOUNTER
builtin functions.


3.1.11: DEFINEMACRO

    DEFINEMACRO is used to define new macros. This function expects
three arguments: 
    
    o  An identifier, being the name of the macro to define. This identifier
may only consist of uppercase or lowercase characters. Note that it can
not contain numbers, nor underscore characters.

o  A number, stating the number of arguments that the macro will require
once it's used. The number must be in the range 0 to 61.

o  The text that the macro expands to, once used. This text may
contain the strings ARGx, x being 1, 2, etc.. At these places the
arguments to the macro are pasted in. The numbers that identify the
arguments are 1 to 9, then A to Z and finally a to z. This gives a range of 61
expandable arguments, which is enough for all real-life applications.

For example, the following fragment defines a macro bookref, which can
be used to typeset a reference to a book. It requires three arguments; say, an
author, a title and the name of a publisher:
        
    DEFINEMACRO(bookref)(3)(
        Author(s):           ARG1
        Book title:          ARG2
        Published by:        ARG3
    )
        
    Such a macro could be used as follows:
        
    bookref(Sobotta/Becher)
           (Atlas der Anatomie des Menschen)
           (Urban und Schwarzenberg, Berlin, 1972)
        
    When called, it would produce the following output:
        
        Author(s):           Sobotta/Becher
        Book title:          Atlas der Anatomie des Menschen
        Published by:        Urban und Schwarzenberg, Berlin, 1972
        
    While applying a macro, the values of the three arguments are pasted to
the places where ARG1, ARG2 etc. occur in the definition.

Note the following when defining new macros:
    
    o  The argument containing the name of the new macro, (bookref) in
the above example, must occur right after DEFINEMACRO. No spaces are
allowed in between. Space characters and newlines may however occur following
this first argument.

This behavior of the yodl program is similar to the usage of the
defined macro: the author information must, enclosed in parentheses, follow
right after the bookref identifier. I implemented this feature to improve
the distinguishing between macros and real text. E.g., a macro me might be
defined, but the text
        
    I like me (but so do you)
        
    still is simple text; the macro me only is activated when a
parenthesis immediately follows it.

o  Be careful when placing newlines or spaces in the definition of a new
macro. E.g., the definition, as given:
        
    DEFINEMACRO(bookref)(3)(
        Author(s):           ARG1
        Book title:          ARG2
        Published by:        ARG3
    )
        
    introduces extra newlines at the beginning and ending of the macro, which
are copied to the output each time the macro is used. The extra newline
occurs, of course, right before the sequence Author(s): and following the
evaluation of ARG3. A simple backslash character at the end of the
DEFINEMACRO line would prevent the insertion of extra newline
characters:
        
    DEFINEMACRO(bookref)(3)(\ 
        Author(s):           ARG1
        Book title:          ARG2
        Published by:        ARG3
    )
        

o  Note that when a macro is used which requires no arguments at all,
one empty argument still must be specified. E.g., my macro package (see
chapter 4) defines a macro it that starts a bullet item in
a list. The macro takes no arguments, but still must be typed as it().

This behavior is consistent: it helps distinguish which identifiers are
macros and which are simple text.

o  Macro arguments may evaluate to text. When a \ is appended to the
macro-argument, or in the default input handling within a non-zero white-space
level (see section 3.1.35) this may invalidate a subsequent macro
call. E.g., the macro
        
    DEFINEMACRO(oops)(1)(
        ARG1
        XXnl()
    )
        
    when called as oops(hello world), produces the output:
        
    hello worldXXnl()
        
    To prevent this gluing to arguments to subsequent macros, a single +
should be prepended to the macro call:
        
    DEFINEMACRO(oops)(1)(
        ARG1
        +XXnl()
    )
        
    See also section 2.2.3 obout the `+identifier'-sequence.

o  Note the preferred layout of macro definitions and macro
calls. Adhere to this form, to prevent drowning in too many parentheses. In
particular:
        
        o  Put all elements of the macro definition on one line, except for
the macro-expansion itself. Each expansion element should be on a line by
itself.
        o  When calling macros put the macro's arguments underneath each
other. If the macrolists themselves contain macro-calls, put each call again
on a line of its own, indenting one tab-position beyond the location of the
opening parenthesis of the argument.
        o  No continnuation backslashes are required between arguments.
        o  With complex calls, indent just the arguments, and put the
parentheses in their required of logical locations.

Example of a complex call:
        
        complex(
            first(
                ARG1
            )(
                ARG2
                +XXnl()
            )
            ARG3
            +nop()
            ARG4
            +XXnl()
        )
            
    o  Macro expansion proceeds as follows:
        
        o  The arguments are read from the input
        o  The contents of the arguments then replace their ARGx
references in the macro's definition (in some exceptional cases, clearly
indicated as such when applicable, the arguments themselves are evaluated
first, and then these evaluated arguments are used as replacements for their
corresponding ARGx references).
        o  The now modified macro is read by Yodl's lexical scanner. This
may result in yet another macro expansion, which will then be evaluated
recursively. 
        o  Eventually, all expansion is completed (well, should complete,
since Yodl doesn't test for eternal recursion) and scanning of the input
continues beyond the original macro call.

For example, assume we have the following two macros:
        
    DEFINEMACRO(First)(1)( 
        Hello ARG1 
        +XXnl() 
    )
    DEFINEMACRO(Second)(1)( 
        First(ARG1) 
        First(ARG1) 
    )
        
    and the following call is issued:
        
    Second(Yodl)
        
    then the following happens:
        
        o  Second(Yodl) is read as encountered.
        o  ARG1 in Second is replaced by Yodl, and the resulting
macro body is sent to the lexical scanner for evaluation: It will see:
        
    First(Yodl)First(Yodl)
        
        o  The first call to First() is now evaluated. This puts
(after replacing ARG1 by Yodl) the following on the scanner's input:
        
    Hello Yodl+XXnl()First(Yodl)
        
        o  Hello Yodl contains no macro call, so it is written to the
output stream. Remains:
        
    +XXnl()First(Yodl)
        
        o  Assume XXnl() merely contains a newline (represented by
\n, here), so +XXnl() is now replaced by \n. This results in the
following input for the lexical scanner: 
        
    \nFirst(Yodl)
        
        o  The \n is now written to the output stream, and the scanner
sees: 
        
    First(Yodl)
        
        o  The second call to First() is now evaluated. This puts
the following on the scanner's input:
        
    Hello Yodl+XXnl()
        
        o  Hello Yodl is written to the output stream. Remains:
        
    +XXnl()
        
        o  +XXnl() is now replaced by \n. The lexical scanner sees:
        
    \n
        
        o  The newline is printed and we're done.


3.1.12: DEFINESYMBOL

    DEFINESYMBOL expects two arguments. An identifier, which is the name of
the symbol to define, and the textual value of the symbol. If the second
argument is empty, the symbol is defined, but has an empty value.

The earlier interpretation of a Yodl symbol as a logical flag can still be
used, but allowing it to obtain textual values greatly simplifies various Yodl
macros. 

Example:
        
    DEFINESYMBOL(Yodl)(Your own document language)
    DEFINESYMBOL(Options)()
        


3.1.13: DELETECHARTABLE

    DELETECHARTABLE removes a definition of a character table that
was defined by DEFINECHARTABLE. This function expects one argument: the
name of the character table remove.

It's an error to attempt to delete a character table that is currently in
use or to attempt to delete a non-existing character table.

Example:
        
    DELETECHARTABLE(mytable)
        


3.1.14: DELETECOUNTER

    DELETECOUNTER removes a definition of a counter that
was defined by DEFINECOUNTER. This function expects one argument: the
name of the counter to remove.

If the counter does not exist, a warning is issued. It is not considered an
error to try to delete a counter that has not been defined earlier.

Example:
        
    DELETECOUNTER(mycounter)
        


3.1.15: DELETEMACRO

    DELETEMACRO removes a definition of a macro that was defined by
DEFINEMACRO. This function takes one argument: the macro name to remove.

There is no error condition (except for syntax errors): when no macro with a
matching name was previously defined, no action is taken.

For example, the safe way to define a macro is by first undefining it. This
ensures that possible previous definitions are removed first:

Example:
        DELETEMACRO(mymacro)
        


3.1.16: DELETENOUSERMACRO

    DELETENOUSERMACRO removes a `nousermacro' definition. The
function expects one argument: the name of the `nousermacro' identifier to be
removed from the nousermacro-set.

There is no error condition (except for syntax errors): when the identifier
wasn't stored as a `nousermacro' no action is taken.

Example:
        DELETENOUSERMACRO(mymacro)
        


3.1.17: DELETESYMBOL

    DELETESYMBOL removes the definition of a symbol variable. It
expects one argument, holding the name of the variable to deleted.

This macro has no error condition (except for syntax errors): the symbol in
question may be previously defined, but that is not necessary.

Example:
        
    DELETESYMBOL(Options)
        


3.1.18: ERROR

    The ERROR function takes one argument: text to display to the standard
error stream. The current input file and line number are also displayed. After
displaying the text, the yodl program aborts with an exit status of 1.

The text passed to the function is expanded first. See the example.

The ERROR function is an example of a function that evaluates its argument
itself.

This command can be used, e.g., in a macro package when an incorrect macro is
expanded. In my macro package (see chapter 4) the ERROR
function is used when the sectioning command chapter() is used in an
article document (in the package, chapter's are only available in
books or reports).

An analogous builtin function is WARNING, which also prints a message but 
does not exit (see section 3.1.70).

Example:
    In the following call, COUNTERVALUE(NTRIES) is replaced by its actual
value: 
        
    ERROR(Stopping after COUNTERVALUE(NTRIES) attempts)
        


3.1.19: EVAL

    The EVAL function takes one argument: the text to be evaluated. This
function allows you to perform an indirect evaluation of Yodl commands. Assume
that there is a symbol varnam containing the name of a counter variable,
then the following displays the counter's value, after having incremented it:
        
    EVAL(NOTRANS(USECOUNTER)(SYMBOLVALUE(varnam)))
        

Here, EVAL performs the following steps:
    
    o  First, NOTRANS(USECOUNTER) is evaluated, producing
        USECOUNTER.
    o  Next, the open parenthesis is processed, producing the open
        parenthesis itself
    o  Then, SYMBOLVALUE(varnam) is evaluated, producing the name of a
        counter, e.g. `counter'.
    o  The closing parentheis is processed, producing the closing
        parenthesis itself.
    o  All this results in the text
        
    USECOUNTER(counter)
        
    o  This text is presented to Yodl's lexical scanner, resulting in
        incrementing the counter, and displaying its incremented value.

b(Caveat): macro arguments themselves are usually not evaluated. So, a
construction like
        
    USECOUNTER(EVAL(SYMBOLVALUE(varnam)))
        
    fails, as `EVAL(SYMBOLVALUE(varnam))' is not a legal name for a
counter. Here the EVAL() call is used as an argument, and is therefore not
expanded. 

The distinction is subtle, and is a consequence of the fact that builtin
functions receive unprocessed arguments. Builtin functions may impose certain
requirements on their arguments (like USECOUNTER requiring the name of a
counter) and these requirements are checked on the arguments as received.

Summarizing: EVAL acts as follows:
    
    o  Its argument is presented to Yodl's lexical scanner
    o  The output produced by the processing of the argument is then
inserted into the input stream in lieu of the original EVAL call.

Most built-in functions do not evaluate their arguments. In fact, only
ERROR, EVAL, FPUTS, INTERNALINDEX, PUSHSUBST, TYPEOUT, UPPERCASE, WARNING
and the iinternally used XXSUBST functions evaluate their arguments.

Postponing evaluations allows you to write:
        
    DEFINESYMBOL(later)(SYMBOLVALUE(earlier))
        
    Eventually, and not when later is defined, a statement like
        
    SYMBOLVALUE(later)
        
    produces the value of earlier at the moment SYMBOLVALUE(later)
is processed. This is, in all its complex consequences, what would be expected
in most cases. It allows us to write general macros producing output that is
only evaluated when the text of symbols and values of arguments become
eventually, rather than when the macro is defined, available. 

Decisions like these invariably result in questions like `what if I have
to define variables using values of other variables?' In those cases
EVAL() must be used. The following example shows the definition of three
symbols: one receives an initial value, two returns one's actual
value when two's value is displayed, three, using EVAL(), stores
one's initial value.

The example also shows yet another way to suppress macro calls, using the
macro nop() which is defined in the all standard conversion types:
        
    DEFINESYMBOL(one)(One's first value)
    DEFINESYMBOL(two)(SYMBOLVALUE(one))
    EVAL(DEFINESYMBOL+nop()(three)(SYMBOLVALUE(one)))
    SETSYMBOL(one)(One's second value)
    "SYMBOLVALUE(two)"      COMMENT(displays "One's second value")
    "SYMBOLVALUE(three)"    COMMENT(displays "One's first value")
        


3.1.20: FILENAME

    The function FILENAME() produces an absolute path to the currently
processed Yodl file. This is not necessarily the canonical path name, as
it may contain current- and parent-path directories.


3.1.21: FPUTS

    The function FPUTS expects two arguments: the first argument is
information to be appended to a file, whose name is given as the second
argument. The first argument is processed by Yodl before it is appended to the
requested filename, so it may contain macro calls.

For example, the following statement appends a countervalue to the
mentioned file:
        
    FPUTS(There have been COUNTERVALUE(attempts) attempts)(/tmp/logfile)
        
    The second argument (name of the file) is not evaluated, but is used as
received. 


3.1.22: IFBUILTIN

    The IFBUILTIN function tests whether its first argument is the name of a
builtin function. If so, the second argument is evaluated, else, the third
argument is evaluated. All three arguments (the variable, the true-list and
the false-list) must be present; though the true-list and/or the false-list
may be empty.

Example:
        
    IFBUILTIN(IFBUILTIN)(\ 
        `BUILTIN' is a builtin - function
    )(\ 
        `BUILTIN' is NOT a builtin - function
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.23: IFCHARTABLE

    The IFCHARTABLE function tests whether its first argument is the name of a
character table. The character table needs not be active.  If the name is the
name of a character table, the second argument is evaluated, else, the third
argument is evaluated. All three arguments (the name, the true list and the
false list) must be present; though the true list and/or the false list may be
empty.

Example:
        
    IFCHARTABLE(standard)(\ 
        `standard' is a character tablebuiltin - function
    )(\ 
        `standard' is NOT a character tablebuiltin - function
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.24: IFDEF

    The IFDEF function tests for the definition status of the argument in its
first argument. If it is a defined entity, the second argument is evaluated,
else, the third argument is evaluated. All three arguments (the entity, the
true list and the false list) must be present; though the true list and/or the
false list may be empty.

The true list is evaluated if the first argument is the name of:
    
    o  a built-in function, or
    o  a character table, or
    o  a counter, or
    o  a no-user-macro symbol, or
    o  a symbol, or
    o  a user-defined macro, or

Example:
        
    IFDEF(someName)(\ 
        `someName' is a defined entity
    )(\ 
        `someName is not defined.
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.25: IFEMPTY

    IFEMPTY expects three arguments: a symbol, a true-list and a
false-list. IFEMPTY evaluates to the true-list if the symbol is an empty
string; otherwise, it evaluates to the false-list.

The function does not further evaluate its argument. Its use is primarily
to test whether a macro has received an argument or not. If the intent is to
check whether a symbol's value is empty or not, IFSTREQUAL [IFSTREQUAL]
should be used, where the first argument is the name of a symbol, and the
second argument is empty.

Example:
        
    IFEMPTY(something)(\ 
        `something' is empty...
    )(\ 
        `something' is not an empty string
    )
        
    In the same way, IFEMPTY can be used to test whether an argument
expands to a non-empty string. A more elaborate example follows below. Say you
want to define a bookref macro to typeset information about an author, a
book title and about the publisher. The publisher information may be absent,
the macro then typesets unknown:
        \ 
    DEFINEMACRO(bookref)(3)(\  
        Author(s):      ARG1
        Title:          ARG2
        Published by:   \ 
        IFEMPTY(ARG3)
        (\ 
            Unknown\ 
        )(\ 
            ARG3\ 
        )
    )
        
    Using the macro, as in:
        \ 
    bookref(Helmut Leonhardt)
           (Histologie, Zytologie und Microanatomie des Menschen)
           ()
        
    would now result in the text Unknown behind the Published by:
line. 

Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.26: IFEQUAL

    IFEQUAL expects four argument lists. It tests whether its first argument
is equal to its second argument. If so, the third argument is evaluated,
else, the fourth argument is evaluated. All four argument lists must be
present, though all can be empty.

The first two arguments of IFEQUAL should be integral numeric
arguments. In order to determine whether the first two arguments are equal,
their values are determined:
    
    o  If the argument starts with an integral numerical value, that value
is the value of the argument.
    o  If the argument is the name of a counter, the counter's value is the
value of the argument
    o  If the values of the first two arguments van be determined
accordingly, their equality determines whether the true list (when the values
are equal) or the false list (when the values are unequal) will be evaluated.
    o  Otherwise, IFEQUAL evaluates the false list.

Example:
        
    IFEQUAL(0)()(\ 
        0 and an empty string are equal
    )(\ 
        0 and an empty string are not equal
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.27: IFGREATER

    IFGREATER expects four argument lists. It tests whether its first argument
is greater than its second argument. If so, the third parameter list is
evaluated, otherwise its fourth argument is evaluated. All four argument lists
must be present, though all can be empty.

The first two arguments of IFGREATER should be integral 
numeric arguments. In order to determine whether the first two arguments are 
equal, their values are determined:
    
    o  If the argument starts with an integral numerical value, that value
is the value of the argument.
    o  If the argument is the name of a counter, the counter's value is the
value of the argument
    o  If the values of the first two arguments van be determined
accordingly, their order relation determines whether the true list (when
the first value is greater than the second value) or the false list (when the
first value is smaller or equal than the second value) is evaluated.
    o  Otherwise, IFGREATER evaluates the false list.

Example:
        
    IFGREATER(counter)(5)(\ 
        counter exceeds the value 5
    )(\ 
        counter does not exceeds the value 5, or counter is no Yodl-counter.
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.28: IFMACRO

    The IFMACRO function tests whether its first argument is the name of a
macro. If the name is the name of a macro, the second argument is evaluated,
else, the third argument is evaluated. All three arguments (the name, the true
list and the false list) must be present; though the true list and/or the
false list may be empty.

Example:
        
    IFMACRO(nested)(\ 
        `nested' is the name of a macro
    )(\ 
        There is no macro named `nested'
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.29: IFSMALLER

    IFSMALLER expects four argument lists. It tests whether its first argument
is smaller than its second argument. If so, the third parameter list is
evaluated, otherwise its fourth argument is evaluated. All four argument lists
must be present, though all can be empty.

The first two arguments of IFSMALLER should be integral numeric
arguments. In order to determine whether the first two arguments are equal,
their values are determined:
    
    o  If the argument starts with an integral numerical value, that value
is the value of the argument.
    o  If the argument is the name of a counter, the counter's value is the
value of the argument
    o  If the values of the first two arguments van be determined
accordingly, their order relation determines whether the true list (when
the first value is smaller than the second value) or the false list (when the
first value is greater than or equal to the second value) is evaluated.
    o  Otherwise, IFSMALLER evaluates the false list.

Example:
        
    IFSMALLER(counter)(5)(\ 
        counter is smaller than the value 5, or counter is no Yodl-counter
    )(\ 
        counter exceeds the value 5
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 


3.1.30: IFSTREQUAL

    IFSTREQUAL tests for the equality of two strings. It expects
four arguments: two strings to match, a true list and a false list. The
true list is only evaluated when the contents of the two string arguments
exactly match. 

The first two arguments of IFSTREQUAL are partially evaluated:
    
    o  If the argument is the name of a symbol, the symbol's value is the
value of the argument
    o  Otherwise, the argument itself is used.

In the degenerate case where the string to be compared is actually the name of
a SYMBOL, use a temporary SYMBOL variable containing the name of that
symbol, and compare it to whatever you want to compare it with. Alternatively,
write a blank space behind the arguments, since the arguments are then
interpreted `as is'. In practice, the need for these constructions seem to
arise seldom, however.

Example:
        
    IFSTREQUAL(MYSYMBOL)(Hello world)(
        The symbol `MYSYMBOL' holds the value `Hello world'
    )(
        The symbol `MYSYMBOL' doesn't hold the value `Hello world'
    )
        


3.1.31: IFSTRSUB

    IFSTRSUB tests whether a string is a sub-string of another 
string. It acts similar to IFSTREQUAL, but
it tests whether the second string is part of the first one. 

The first two arguments of IFSTREQULA are partially evaluated:
    
    o  If the argument is the name of a symbol, the symbol's value is the
value of the argument
    o  Otherwise, the argument itself is used.

In the degenerate case where the string to be compared is actually the name of
a SYMBOL, use a temporary SYMBOL variable containing the name of that
symbol, and compare it to whatever you want to compare it with. Alternatively,
write a blank space behind the arguments, since the arguments are then
interpreted `as is'. In practice, the need for these constructions seem to
arise seldom, however.

Example:
    
        IFSTRSUB(haystack)(needle)(
            `needle' was found in `haystack'
        )(
            `needle' was not found in `haystack'
        )
    
    Note that both `haystack' and `needle' may be the names of symbols. If
they are, their contents are is compared, rather than the literal names
`haystack' and `needle'


3.1.32: IFSYMBOL

    The IFSYMBOL function tests whether its first argument is the name of a
symbol. If it is the name of a symbol, the second argument is evaluated,
otherwise the third argument is evaluated. All three arguments (the name, the
true list and the false list) must be present; though the true list and/or the
false list may be empty.

Example:
        
    IFSYMBOL(nested)(\ 
        `nested' is the name of a symbol
    )(\ 
        There is no symbol named `nested'
    )
        
    Please note the preferred layout: The first argument immediately follows
the function name, then the second argument (the true list) is indented,
as is the false list. The layout closely follows the preferred layout of
if-else statements of many programming languages. 

C(  FBB consider additive expressions   )
    
3.1.33: IFZERO

    IFZERO expects three arguments. If the first argument is zero (0)
the function expands to the true list (the second argument). Otherwise it
expands to the false list (the third argument).

The first argument of IFZERO should be an integral numeric value. Its
value is determined as follows:
    
    o  If the argument starts with an integral numerical value, that value
is the value of the argument.
    o  If the argument is the name of a counter, the counter's value is the
value of the argument
    o  Otherwise, the first arguments evaluates as 0, and the false list is
used.

Note that, starting with Yodl version 2.00 the first argument is not
evaluated. So COUNTERVALUE(somecounter) always evaluates as 0. If the
value of a counter is required, simply provide its name as the first argument
of the IFZERO function.

Example:
        
    DEFINEMACRO(environment)(2)(\ 
        IFZERO(ARG2)(\ 
            NOEXPAND(\end{ARG1})\ 
        )(\  
            NOEXPAND(\begin{ARG1})\ 
        )\ 
    )    
        
    Such a macro may be used as follows:
        
    environment(center)(1)
        Now comes centered text.
    environment(center)(0)
        
    which would of course lead to \begin and \end{center}. The numeric
second argument is used here as a on/off switch.


3.1.34: INCLUDEFILE

    INCLUDEFILE takes one argument, a filename. The file is processed by
Yodl. If a file should be inserted without processing the builtin function
NOEXPANDINCLUDE [NOEXPANDINCLUDE] or
NOEXPANDPATHINCLUDE [NOEXPANDPATHINCLUDE] should be used.

The yodl program supplies, when necessary, an extension to the filename.
The supplied extension is .yo, unless defined otherwise during the
compilation of the program. 

Furthermore, Yodl tries to locate the file in the Yodl's include path (which
may be set using the --include option). The actual value of the include
path is shown in the usage information, displayed when Yodl is started without
arguments.

Example:
        
    INCLUDEFILE(latex)
        
    Here, Yodl attempts to include the file latex or latex.yo from the
current include path. When the file is not found, Yodl aborts.


3.1.35: INCWSLEVEL

    INCWSLEVEL requires one (empty) argument. 

It increments the current white-space level. The white-space level typically
is used in files that only define Yodl macros. When no output should be
generated while processing these files, the white-space level can be used to
check for this. If the white-space level exceeds zero, a warning is generated
if the file produces non-whitespace output. The builtin function
DECWSLEVEL is used to decrement the whitespace level following a previous
INCWSLEVEL call.

Once the white space level exceeds zero, no output is generated. White
space, therefore is effectively ignored. The white space level cannot be
reduced to negative values. A warning is issued if that would have happened if
it were allowed.

Example:
        
    INCWSLEVEL()
    DEFINESYMBOL(....)
    DEFINEMACRO(...)(...)(...)
    DECWSLEVEL()
        
    Without the INCWSLEVEL and DECWSLEVEL, calls, 
the above definition would generate four empty lines to the output stream.

The INCWSLEVEL and DECWSLEVEL calls may be nested. The best
approach is to put an INCWSLEVEL at the first line of a macro-defining
Yodl-file, and a matching DECWSLEVEL call at the very last line.


3.1.36: INTERNALINDEX

    INTERNALINDEX expects one argument list. The argument list is evaluated
and written to the index file.

The index file is defined since Yodl version 2.00, and contains the fixup
information which was previously written to Yodl's output as the
.tt(Yodl)TAGSTART.  ... .tt(Yodl)TAGEND. sequence. 

The index file allows for greater processing speed, at the expense of an
additional file. The associated yodlpost postprocessing program reads
and processes the index file, and modifies the corresponding yodl-output
accordingly. 

The index file is not created when output is written to the standard output
name, since Yodl is unable to request the system for the current file offset.

The entries of the index file always fit on one line. INTERNALINDEX
changes newline characters in its argument into single blank spaces. Each line
starts with the current offset of Yodl's output file, thus indicating the
exact location where a fixup is requested. An example of a produced fixup line
could be
        
    3004 ref MACROPACKAGE
        
    indicating that at offset 3004 in the produced output file a reference to
the label MACROPACKAGE is requested. Assuming a html conversion, 
The postprocessor thereupon
writes something like 
        
    <a href="outfile04.html#MACROPACKAGE">4.3.2.</a>
        
    into the actual output file while processing Yodl's output up to 
offset location 3004.

Consequently, producing Yodl-output normally consists of two steps:
    
    o  First, Yodl itself is started, producing, e.g., out.idx (the
index file) and out.yodl (Yodl's raw output).
    o  Then, Yodl's post-processor processes out.idx 
and out.yodl, producing one or more final output files, in which the
elements of the index file have been properly handled. This may result in
multiple output file, like report.html, report01.html, report02.html etc.


3.1.37: NOEXPAND

    NOEXPAND is used to send text to the final output file without being
expanded by Yodl (the other methods are the CHAR macro, see section
3.1.4, and the NOTRANS macro, see section 3.1.40).  NOEXPAND
takes one argument, the text in question. Whatever occurs in the
argument is not subject to parsing or expansion by Yodl, but is simply copied
to the output file (except for CHAR and (iinternally used) XXSUBST
functions in the argument, which are expanded. If CHAR-expansion is
not required either NOTRANS [NOTRANS] can be used).

Furthermore, the contents of the argument are also subject to
character table translations, using the currently active table. This should
come as no surprise. Ignoring character tables would make both the processing
of CHAR calls and the NOTRANS function superfluous. 

So, the following situations are recognized:
    

        

   2 

   2 


     Macro expansion   yes   no 


 Yes   (standard)   Push chartable 

                    (standard) 

                    Pop chartable 

 No    NOEXPAND     NOTRANS 





E.g., let's assume that you need to write in your document the following text:
        
    INCLUDEFILE(something or the other)
    IFDEF(onething)(
        ...
    )(
        ....
    )
    NOEXPAND(whatever)
        

The way to accomplish this is by prefixing the text by NOEXPAND followed
by an open parenthesis, and by postfixing it by a closing parenthesis.
Otherwise, the text would be expanded by Yodl while processing it (and would
lead to syntax errors, since the text isn't correct in the sense of the Yodl
language).

For this function, keep the following caveats in mind:
    
    o  There is only one thing that a NOEXPAND cannot protect from 
    expansion: an ARGx in a macro definition. The argument specifier 
    is always processed. E.g., after
        
    DEFINEMACRO(thatsit)(1)(
        That is --> NOEXPAND(ARG1) <-- it!
    )
    thatsit(after all)
        
    the ARG1 inside the NOEXPAND statement is replaced with 
        after all.
    o  The NOEXPAND function must, as all functions, be followed by a 
    argument. The parentheses of the list must therefore be `balanced'. 
    For unbalanced lists, use CHAR(40) to set an open parenthesis, 
    or CHAR(41) to typeset a closing parenthesis.


3.1.38: NOEXPANDINCLUDE

    NOEXPANDINCLUDE takes one argument, a filename. The file is
included. 

The filename is uses as specified. The include path is not used when locating
this file.

The argument to NOEXPANDINCLUDE is partially evaluated:
    
    o  If the argument is the name of a symbol, the symbol's value is the
value of the argument
    o  Otherwise, the argument itself is used.

The thus obtained file name is not further evaluated: in particular, it
is not affected by available character translations.

The contents of the file are included literally, not subject to
macro expansion. Character translations are performed, though. If character
translations are not appropriate, PUSHCHARTABLE can be
used to suppress character table translations temporarily.

The purpose of NOEXPANDINCLUDE is to include source code literally in the
document, as in:
        
    NOEXPANDINCLUDE(literal.c)
        
    The function NOEXPANDPATHINCLUDE can be used to
insert a file which is located in one of the directories specified in
Yodl's include path.


3.1.39: NOEXPANDPATHINCLUDE

    NOEXPANDPATHINCLUDE takes one argument, a filename. The file is
included. The file is searched for in the directories specified in Yodl's
includepath. 

The argument to NOEXPANDPATHINCLUDE is partially evaluated:
    
    o  If the argument is the name of a symbol, the symbol's value is the
value of the argument
    o  Otherwise, the argument itself is used.

The thus obtained file name is not further evaluated: in particular, it
is not affected by available character translations.

Like the NOEXPANDINCLUDE function, the contents of the file are included
literally, not subject to macro expansion. Character translations are
performed, though. If character translations are not appropriate,
PUSHCHARTABLE [PUSHCHARTABLE] can be used to suppress character table
translations temporarily.

The purpose of NOEXPANDPATHINCLUDE is to include source code as defined in a
macro package literally into the document, as in:
        
    NOEXPANDPATHINCLUDE(rug-menubegin.xml)
        


3.1.40: NOTRANS

    NOTRANS copies its one argument literally to the output file, without
expanding macros in it and without translating the characters with the current
translation table. The NOTRANS function is typically used to send commands
for the output format to the output file.

For example, consider the following code fragment:
        
    COMMENT(--- Define character translations for \, { and } in LaTeX. ---)
    DEFINECHARTABLE(standard)(
        '\\'    =    "$\\backslash$"
        '{'     =    "\\verb+{+"
        '}'     =    "\\verb+}+"
    )
    
    COMMENT(--- Activate the translation table. ---)
    USECHARTABLE(standard)
    
    COMMENT(--- Now two tests: ---)
    
    NOEXPAND(\input{epsf.tex})
    NOTRANS(\input{epsf.tex})
        
    NOEXPAND sends 
        
    $\backslash$input\verb+{+epsf.tex\verb+}+
        
    since the characters in its argument are translated with the standard 
translation table. In contrast, NOTRANS sends \input{epsf.tex}.

The argument of NOTRANS must be balanced with respect to its
parentheses. When using an unbalanced set of parentheses, use
CHAR(40) to send a literal (, or CHAR(41) to send a
).

While converting Yodl-documents to target document types Yodl frequently uses
the (not further documented) builtin function XXSUBST. In the
unlikely event that the text XXSUBST(...) must be written
in a document, the sequence
    
    XXSUBST+CHAR(40)...CHAR(41)
    
    can be used.

The NOEXPAND description summarizes all combinations of
character translations and/or macro expansion, and how they are handled and
realized by Yodl.


3.1.41: NOUSERMACRO

    NOUSERMACRO controls yodl's warnings in the following way: When Yodl
is started with the -w flag on the command line, warnings are generated
when Yodl encounters a possible macro name, i.e., a name that is followed by a
parenthesized argument, while no macro by that name has been defined.  Yodl
then prints something like cannot expand possible user macro.

Examples of such sequences are, The necessary file(s) are in
/usr/local/lib/yodl, or see the manual page for sed(1). The candidate
macros are file and sed; these names could just as well be `valid'
user macros followed by their argument.

When a corresponding NOUSERMACRO statement appears before yodl 
encounters the candidate macros, no warning is generated. A fragment might 
therefore be:
        
    NOUSERMACRO(file sed)
    The necessary file(s) are in ...
    See the manual page for sed(1).
        
    The NOUSERMACRO accepts one or more names in its argument, separated
by white space, commas, colons, or semi-colons.


3.1.42: OUTBASE

    OUTBASE inserts the current basename of the output file into the output
file. The basename is the name of the file of which the directory components
and extension were stripped.

If the output file is the standard output file, - is inserted.


3.1.43: OUTDIR

    OUTDIR inserts the current path name of the output file into the output
file. The path name is a, not necessarily absolute, designator of the
directory in which the output file is located. If the output file is indicated
as, e.g., -o out, then OUTDIR simply inserts a dot.

If the output file is the standard output file, a dot is inserted too.


3.1.44: OUTFILENAME

    OUTFILENAME inserts the current filename of the output file into the
output file. The filename is the name of the file of which the directory
components  were stripped.

If the output file is the standard output file, - is inserted.


3.1.45: PARAGRAPH

    PARAGRAPH isn't really a builtin function, but as Yodl handles 
paragraphs in a special way it is probably useful to describe paragraph
handling here nonetheless. 
Starting with Yodl 2.00  PARAGRAPH operates as follows:

If the macro is not defined, new paragraphs, defined as series of consecutive
empty lines written to the output stream, are not handled different from any
other series of characters sent to the output stream. I.e., they are inserted
into that stream.

However, if the macro has been defined, Yodl calls it
whenever a new paragraph (defined as a series of at least two blank lines)
has been recognized.

The empty lines that were actually recognized may be obtained inside the
PARAGRAPH macro from the XXparagraph symbol, if this symbol has
been be defined by that time. If defined, it contains the white space that
caused Yodl to call the PARAGRAPH macro.

Note that, in order to inspect XXparagraph it must have been defined
first. Yodl itself does not define this symbol itself.

The PARAGRAPH macro should be  defined as a macro not expecting arguments.
The macro is thus given a chance to process the paragraph in a way that's
fitting for the particular conversion type. If the PARAGRAPH macro
produces series of empty lines itself, then those empty lines do not
cause Yodl to activate PARAGRAPH. So, Yodl itself will not recursively
call PARAGRAPH, although the macro could call itself recursively. Of
course, such recursive activcation of PARAGRAPH is then the sole
responsibility of the macro's author, and not Yodl's.

Some document languages do not need paragraph starts; e.g., LaTeX handles its
own paragraphs. Other document languages do need it: typically, PARAGRAPH
is then defined in a macro file to trigger some special action. E.g., a HTML
converter might define a paragraph as:
        
    DEFINEMACRO(PARAGRAPH)(0)(
        XXnl()
        NOTRANS(<p>)
    )
        
    A system like xml has more strict requirements. Paragraphs here must be
opened and closed using pairs of 
 and 
 tags. In those cases an
auxiliary counter can be used to indicate whether there is an open paragraph
or not. The PARAGRAPH macro could check for this as follows, assuming the
availability of a counter XXp:
        
    DEFINEMACRO(PARAGRAPH)(0)(
        XXnl()
        IFZERO(XXp)(
        )(
            NOTRANS(</p>)
        )
        NOTRANS(<p>)
        SETCOUNTER(XXp)(1)
    )
        
    Note that the above fragment exemplifies an approach, not necessarily
the implementation of the PARAGRAPH macro for an xml-converter.


3.1.46: PIPETHROUGH

    The builtin function PIPETHROUGH is, besides SYSTEM, the second
function with which a Yodl document can affect its
environment. PIPETHROUGH can be very useful. It uses an external program
to accomplish special features. The idea is that an external command is
started, to which a block of text from within a Yodl document is `piped'. The
output of that child program is piped back into the Yodl document; hence, a
block of text is `piped through' an external program.  Whatever is received
again in the Yodl run, is further processed.

The PIPETHROUGH function takes two arguments:

o  the command to run, and

o  the text to send to that command.

Functionally, the occurrence of the PIPETHROUGH function and of its two
arguments is replaced by whatever the child program produces on its standard
output. 

An example might be the inclusion of the current date, as in:

The current date is:
PIPETHROUGH(date)()

In this example the command is date and the text to send to that program is
empty.

The main purpose of this function is to provide a way by which external programs
can be used to create, e.g., tables or figures for a given output format.
Further releases of Yodl may contain such dedicated programs for the output
formats. 


3.1.47: POPCHARTABLE

    Character tables which are pushed onto the table stack using
PUSHCHARTABLE() are restored (popped) using POPCHARTABLE(). For a
description of this mechanism please refer to section 2.3.3.


3.1.48: POPCOUNTER

    POPCOUNTER is used to remove the topmost counter from the counter stack. 
The values of counters may be pushed on a stack using
PUSHCOUNTER [PUSHCOUNTER]. To remove the topmost element of a counter's
stack POPCOUNTER is available. POPCOUNTER expects one argument: the
name of the counter to pop. The previously pushed value then becomes the new
value of the counter. A counter's value may be popped after defining it,
whereafter the stack is empty, but the counter will still be defined. In
that case, using the counter's value is considered an error. 

Examples:
        
    DEFINECOUNTER(YEAR)(1950)
    POPCOUNTER(YEAR)
    COMMENT(YEAR now has an undefined value)
        
    See also section 2.5.


3.1.49: POPMACRO

    POPMACRO is used to remove the actual macro definition, restoring a
previously pushed definition.  The values of macros may be pushed on a stack
using PUSHMACRO. 

To remove the topmost element of a macro's stack POPMACRO is
available. POPMACRO expects one argument: the name of the macro to
pop. The previously pushed value then becomes the new value of the macro.

A macro's value may be popped after defining it, after which its stack is
empty. In that case, using the macro (although the macro's name is still
defined) is considered an error.

Example:
        
    DEFINEMACRO(Hello)(1)(Hello, ARG1, this is a macro definition)
    Hello(Karel)
    PUSHMACRO(Hello)(1)(Hello, ARG1, this is the new definition)
    Hello(Karel)
    POPMACRO(Hello)
    Hello(Karel)
    COMMENT(The third activation of Hello() produces the same output
            as the first activation)
        


3.1.50: POPSUBST

    POPSUBST is used to revert to a previous level of interpretation of
SUBST definitions. Refer to the descriptions of the PUSHSUBST and
SUBST builtin commands below for details. 

There is no limit to the number of times POPSUBST can be called. Once the
`PUSHSUBST stack' is empty SUBST definitions are automatically 
interpreted  (so no stack-underflow error is ever encountered).


3.1.51: POPSYMBOL

    POPSYMBOL is used to remove the topmost symbol from the symbol stack. 
The values of symbols may be pushed on a stack using
PUSHSYMBOL [PUSHSYMBOL]. To remove the topmost element of a symbol's
stack POPSYMBOL is available. 

POPSYMBOL expects one argument: the name of the symbol to pop. The
previously pushed value then becomes the new value of the symbol. 

A symbol's value may be popped after defining it, after which its stack is
empty. In that case, using the symbol (although the symbol's name is still
defined) is considered an error.

Example:
        
    DEFINESYMBOL(YEAR)(This happened in 1950)
    POPSYMBOL(YEAR)
    COMMENT(YEAR now has an undefined value)
        


3.1.52: POPWSLEVEL

    POPWSLEVEL is used to remove the topmost wslevel from the wslevel stack.
The values of wslevels may be pushed on a stack using
PUSHWSLEVEL [PUSHWSLEVEL]. See also section DECWSLEVEL [DECWSLEVEL]

To remove the topmost element of a wslevel's stack POPWSLEVEL is
available. POPWSLEVEL expects one argument: the name of the wslevel to
pop. The previously pushed value then becomes the new value of the wslevel. A
wslevel's value may be popped after defining it, emptying the stack, but the
wslevel will still be defined. In that case, using the wslevel's value is
considered an error.

Example:
        
    COMMENT(Assume WS level is zero)
    
    PUSHWSLEVEL(1)
    COMMENT(WS level now equals 1)

    POPWSLEVEL()
    COMMENT(WS level now equals 0 again)
        


3.1.53: PUSHCHARTABLE

    Once a character table has been defined, it can be pushed onto a stack
using PUSHCHARTABLE. The pushed chartable may be popped
later. PUSHCHARTABLE is described in more detail in section
2.3.3.


3.1.54: PUSHCOUNTER

    PUSHCOUNTER is used to start another lifetime for a counter, pushing its
current value on a stack. A stack is available for each individual counter.

PUSHCOUNTER expects two arguments: the name of the counter to push and 
an additive expression whose value becomes the counter's new value (after
pushing the current value)

The additive expression may not contain blank spaces and may use + and -
operators, its operands may either be integral numeric values or names of
(defined) counters.  The resulting value can be negative; in that case, a
value is subtracted from the destination counter.

When the second argument is empty, then the new value will be zero.  Specify
the name of the counter twice to merely push its value, without modifying its
current value.

Examples:
        
    DEFINECOUNTER(YEAR)(1950)
    PUSHCOUNTER(YEAR)(1962)
    COMMENT(YEAR now has the value 1962, and a pushed value of 1950)
        
    See also section 2.5.


3.1.55: PUSHMACRO

    PUSHMACRO is used to start another lifetime for a macro, pushing its
current definition on a stack. A stack is available for each individual macro.

PUSHMACRO expects three arguments: the name of the macro to push, the
number of its arguments after pushing (which may be different from the number
of arguments interpreted by the pushed macro)  and its new
definition. 

So, PUSHMACRO is used exactly like DEFINEMACRO, but
redefines a current macro (or define a new macro if no macro was defined by
the name specified as its first argument.

Example:
        
    DEFINEMACRO(Hello)(1)(Hello, ARG1, this is a macro definition)
    Hello(Karel)
    PUSHMACRO(Hello)(1)(Hello, ARG1, this is the new definition)
    Hello(Karel)
    POPMACRO(Hello)
    Hello(Karel)
    COMMENT(The third activation of Hello() produces the same output
            as the first activation)
        


3.1.56: PUSHSUBST

    PUSHSUBST can be used to (temporarily) suppress the interpretation of
SUBST definitions (the SUBST built-in command is covered
below, refer to its description for an example). 

PUSHSUBST expects one argument: an integral number which is either 0 or
non-zero (commonly: 1). After calling PUSHSUBST(0) SUBST
definitions are not interpreted anymore; use POPSUBST() to revert to
the previous type of interpretation. Alternatively, PUSHSUBST(0) can
be used to stack another level of SUBST interpretations on top of the
last-used one.

On a 64-bit computer the PUSHSUBST stack can hold slightly more than 60
SUBST interpretation levels. When more levels are pushed, the oldest levels
are silently forgotten. Calling POPSUBST once the PUSHSUBST stack is
empty results in activating the SUBST interpretations (and so a
stack-underflow error will not be encountered).


3.1.57: PUSHSYMBOL

    PUSHSYMBOL is used to start another lifetime for a symbol, pushing its
current value on a stack. A stack is available for each individual symbol.

PUSHSYMBOL expects two arguments: the name of the symbol to push and its
new text after pushing. When the second argument is an empty argument, the new
text will be empty. The new text may be specified as a literal text, or as the
name of an existing symbol. Specify the name of the symbol twice to merely
push its value, without modifying its current value.

Examples:
        
    DEFINESYMBOL(YEAR)(This happened in 1950)
    PUSHSYMBOL(YEAR)(This happened in 1962)
    COMMENT(YEAR now has the value `This happened in 1962' and a 
            pushed value of `This happened in 1950')
        


3.1.58: PUSHWSLEVEL

    PUSHWSLEVEL is used to start another lifetime of the white-space level
pushing the level's current value on a stack. See also section 
INCWSLEVEL [INCWSLEVEL]

PUSHWSLEVEL expects one argument, the new value of the white-space
level. This value may be specified as a numerical value or as the name of a
counter. The argument may be empty, in which case the new value will be 
zero. 

Example:
        
    COMMENT(Assume WS level is zero)
    
    PUSHWSLEVEL(1)
    COMMENT(WS level now equals 1)

    POPWSLEVEL()
    COMMENT(WS level now equals 0 again)
        


3.1.59: RENAMEMACRO

    RENAMEMACRO takes two arguments: the name of a built-in macro
(such as INCLUDEFILE) and its new name.

E.g., after
        
    RENAMEMACRO(INCLUDEFILE)(include)
        

a file must be included by include(file).  INCLUDEFILE can no
longer be used for this: following the RENAMEMACRO action, the old name
can no longer be used; it becomes an undefined symbol.

If you want to make an alias for a built-in command, do it with 
DEFINEMACRO. E.g., after:
        
    DEFINEMACRO(include)(1)(INCLUDEFILE(ARG1))
        
both INCLUDEFILE and include can be used to include a file.


3.1.60: SETCOUNTER

    SETCOUNTER expects two arguments: the name of a counter, and an additive
expression defining the value to assign. The counter must be previously
created with DEFINECOUNTER.

The additive expression may not contain blank spaces and may use + and -
operators, its operands may either be integral numeric values or names of
(defined) counters.  The resulting value can be negative; in that case, a
negative value is assigned to the destination counter.

For example, if one and two are counters, then 
        
    SETTOCOUNTER(one)(-two)\//    assigns -two's value to one
    SETTOCOUNTER(one)(two+two)\// assigns 2 x two's value to one
        

See also section 2.5.


3.1.61: SETSYMBOL

    SETSYMBOL expects two arguments: the name of a symbol, and
the text to assign to the named symbol. The symbol must previously have been
defined by DEFINESYMBOL.


3.1.62: SUBST

    SUBST is a general-purpose substitution mechanism for strings appearing in
the input. SUBST takes two arguments: a search string and a substitution
string.  E.g., after
        
    SUBST(VERSION)(1.00)
         
    Yodl transforms all occurrences of VERSION in its input into 
1.00.

SUBST is also useful in situations where multi-character sequences
should be converted to accented characters. E.g., a LaTeX converter might
define:
        
    SUBST('e)(+NOTRANS(\'{e}))
        
    Each 'e in the input will subsequently be converted to e. 

SUBST may be used in combination with the command line 
flag -P, as in a invocation
        
    yodl2html -P'SUBST(VERSION)(1.00)' myfile.yo
        

Another useful substitution might be:
        
    SUBST(_OP_)(CHAR(40))
    SUBST(_CP_)(CHAR(41))
        

which defines an opening parenthesis (_OP_) and a closing parenthesis
(_CP_) as mapped to the CHAR function. The strings _OP_ and
_CP_ might then be used to produce unbalanced arguments.

Note that:
    
    o  The first argument of the SUBST command, the search string, is
taken literally. Yodl does not expand it; the string must be literally
matched in the input.
    o  The second argument, the replacement, is further processed by Yodl. 
Protect this text by NOTRANS or NOEXPAND where appropriate.

Substitutions occur extremely early while Yodl processes its input files. In
order to process its input files, Yodl takes the following steps:
    
    1.  It requests input from its lexical scanner (so-called tokens)
    2.  Its parser processes the tokens produced by the lexical scanner
    3.  Its parser may send text to an output `object', which 
eventually appears in the output file generated by Yodl.
    
    Yodl performs all macro substitutions in step 2, and all character
table conversions in step 3. However, the lexical scanner has access to the
SUBST definitions: as soon as its lexical analyzer detects a series of
characters matching the defining sequence of a SUBST definition, it 
replaces that defining sequence by its definition. That definition is then
again read by the lexical scanner. Of course, this definition may, in turn,
contain defining sequences of other SUBST definitions: these are then 
replaced by their definitions as well. This implies:
    
    o  Circular definitions may cause the lexical scanner to get stuck in a
replacement loop. It is the responsibility of the author defining SUBST
definitions to make sure that this doesn't happen.
    o  Neither the parser, nor the output object ever sees the SUBST
defining character sequences: they only see their definitions.

In some cases substitutions must be suppressed. Consider double
quoted text strings that are frequently used in programming
languages. E.g., "hello world". The text inside the string should not be
converted by Yodl, but unless substitutions can be suppressed the string
    "\"evil code"
    appears as
    "evil code"
    
To suppress the interpretation of SUBST definitions PUSHSUBST,
introduced earlier, can be used. The predefined macro verb suppresses the
interpretation of SUBST definitions by starting with PUSHSUBST(0)
and ending with POPSUBST().


3.1.63: SYMBOLVALUE

    SYMBOLVALUE expands to the value of a symbol. Its single argument
must be the name of a symbol.  The symbol must have been created earlier
using DEFINESYMBOL.
    
   
    Example:
        
    The symbol has value SYMBOLVALUE(MYSYMBOL).
        


3.1.64: SYSTEM

    SYSTEM takes one argument: a command to execute. The command is run via
the standard C function system. 

SYSTEM can be useful in many ways. E.g., you might want to log when
someone processes your document, as in:
        
    SYSTEM(echo Document processed! | mail myself@my.host)
        
    Note that SYSTEM merely performs an system-related task. It's a
process that is separated from the Yodl process itself. One of the
consequences of this is that any output generated by SYSTEM not
normally appears into Yodl's output file. If the output of a subprocess should
be inserted into Yodl's output file, either use
PIPETHROUGH [PIPETHROUGH], or insert a temporary file as shown in the
following example:
        
    SYSTEM(date > datefile)
    The current date is: 
    INCLUDEFILE(datefile)
    SYSTEM(rm datefile)
        


3.1.65: TYPEOUT

    TYPEOUT requires one argument. The text of the list is sent to the
standard error stream, followed by a newline. This feature can be handy to
show, e.g., messages such as version numbers in macro package files.

Example: The following macro includes a file and writes to the screen that
this file is currently processed.
        
    DEFINEMACRO(includefile)(1)(
        TYPEOUT(About to process document: ARG1)
        INCLUDEFILE(ARG1)
    )
        


3.1.66: UPPERCASE

    UPPERCASE converts a string or a part of it to upper case. It has
two arguments:
    
    o  The string to convert;
    o  A length, indicating how many characters (starting from the beginning
of the string) should be converted.

The length indicator can be smaller than one or larger than the length of
the string; in that case, the whole string is convertered.

Example:
        
    UPPERCASE(hello world)(1)
    UPPERCASE(hello world)(5)
    UPPERCASE(hello world)(0)
        
    This code sample expands to:
        
    Hello world
    HELLO world
    HELLO WORLD
        


3.1.67: USECHARTABLE

    USECHARTABLE takes one argument: the name of a translation table to
activate. The table must previously have been defined using
DEFINECHARTABLE. See section 2.3 for a description of
character translation tables.

Alternatively, the name may be empty in which case the default character
mapping is restored.


3.1.68: USECOUNTER

    USECOUNTER is a combination of ADDTOCOUNTER and COUNTERVALUE. It
expects one argument: the name of an defined counter (see
DEFINECOUNTER [DEFINECOUNTER]).

The counter is first incremented by 1. Then the function expands to 
the counter's value.

See also section 2.5.


3.1.69: VERBOSITY

    VERBOSITY expects two arguments, and may be used to change the verbosity
level inside Yodl files. The function may be used profitably for debugging
purposes, to debug the expansion of a macro or the processing of a Yodl input
file. 

The first argument indicates the processing mode of the second argument, and it
may be:
    
    o  Empty, in which case the message-level is set to the value specified
in the second argument;
    o  +, in which case the value specified in the second argument
augments the current message level;
    o  -, in which case the value specified in the second argument
augments is removed from the current message level

The second argument specifies one or more, separated by blanks, message
level names or it may be set to a hexadecimal value (starting with 0x),
using hexadecimal values to represent message levels. Also, NONE may be
used, to specify no message level, or ALL can be used to specify all
message levels. 

The following message levels are defined:
    
    o  ALERT (0x40). When an alert-error occurs, Yodl
terminates. Here Yodl requests something of the system (like a get_cwd()),
but the system fails.
    o  CRITICAL (0x20). When a critical error occurs, Yodl
terminates.  The message itself can be suppressed, but exiting can't. A
critical condition is, e.g., the omission of an open parenthesis at a location
where a parenthesized argument should appear, or a non-existing file in an
INCLUDEFILE specification (as this file should be parsed). A non-existing
file with a NOEXPANDINCLUDE specification is a plain (non-critical) error.
    o  DEBUG (0x01). Probably too much info, like getting information
about each character that was read by Yodl.
    o  ERROR (0x10). An error (like doubly defined symbols). Error
messages will not stop the parsing of the input (up to a maximum number of
errors), but no output is generated.
    o  INFO (0x02). Not as detailed as `debug', but still very much
info, like information about media switches.
    o  NOTICE (0x04). Information about, e.g., calls to the builtin
function calls.
    o  WARNING (0x08). Something you should know about, but probably
not affecting Yodl's proper functioning

There also exists a level EMERG (0x80) which cannot be suppressed.

The value 0x00 represents NONE, the value 0xff represents
ALL. 

When specifying multiple message levels using the hexadecimal form, their
hexadecimal values should be binary-or-ed: adding them is ok, as long as you
don't specify ALL:
        
    VERBOSITY()(0x06)
    COMMENT(this specifies `INFO' and `NOTICE')
        
    When specifying message levels by their names, the names may be truncated
at a unique point. However, the message level names are interpreted case
sensitively, so INF for INFO is recognized as such, but info for
INFO isn't. The following examples all specify verbosity levels INFO and
NOTICE: 
        
    VERBOSITY()(I N)
    VERBOSITY()(N I)
    VERBOSITY()(NOT IN)
    VERBOSITY()(INFO NOTICE)
        


3.1.70: WARNING

    WARNING takes one argument: text to display as a warning. The 
yodl program makes sure that before showing the text, the current file and 
line number are printed. Other than this, WARNING works just as
TYPEOUT (see section 3.1.65). 

Note that an analogous function ERROR exists, which prints a message and
then terminates the program (see section 3.1.18).


Chapter 4: Macros and Document types

The macro package distributed with Yodl is described in
this chapter. The macro package consists of a number of definition files,
which convert a Yodl document that follows a certain syntax to an output
format. The main output formats, currently supported, are:
    
    o  HTML;
    o  LaTeX (plain LaTeX, no latex2e);
    o  The groff `man' format which is used for man pages;
    o  The groff `ms' format which is more expressive;
    o  Basic, plain text 

The following conversion format is in an experimental stage:
    
    o  XML, as used by the University of Groningen's so-called
`webplatform'. 

Currently discontinued conversion formats are:
    
    o  SGML, although the basic macros are available. SGML can probably be
reactivated fairly quickly. Contact the maintainer if support for SGML should
be reinstated
    o  texinfo, mainly due to the fact that the current maintainer doesn't
know what the required post-processing actions are.
    o  tely, since this conversion format is unknown to the current
maintainer.

Other formats may be available, but maybe in an unstable state. Contact
the the maintainer if you have a new format to add, or want to reanimate
formats that were previously available.


4.1: General structure of a Yodl document

    This section describes the general format of a Yodl document.

First of all, a Yodl document needs a preamble. This part
of the document must be at the top, and must define the modifiers and the  
document type. Modifiers, when present, must appear first.

Modifiers are often specific for a particular target document type 
(e.g., latexoptions or mailto), but may also have a general nature
(e.g., affiliation or abstract). All modifiers are used to modify
parameters of document types. Therefore, they must be specified before the
document type is defined.

All modifiers are listed in section 4.3.7. In general, you should use
as many modifiers as appropriate. E.g., you should define a mailto even
when you're not planning to convert your document to HTML. The reason is
twofold: first, you might later decide that a HTML version isn't a bad idea
after all. Second, later versions of the converters might use mailto even
for non-HTML output formats.

Following the modifiers, the document type is defined. The document type
is either article, report, book, plainhtml or manpage.
Except for the manpage document type, which is a highly specialized
document type, described in section 4.1.2, the following rules apply:

A decision about the document type to use should be based on its
complexity. If the document's organization becomes too complex, it is probably
a good idea to use a document type supporting a more complex
organization. E.g., a complex article might be written as an accessible
report, combining related sections into chapters. Similarly, the structure
of a report having 30 chapters might improve when it's re-organized as a
book having parts. To offer a rule of thumb: a document should have no
more than approximately ten top-level sections, and each top-level sectioning
should have no more than approximately ten subsections, etc..

The document type influences the way Yodl formats the output. An article
(or plainhtml) results in one output file. E.g., one final document when
converting to HTML. If your article is way too long, then the loading of the
HTML document also requires much time. When converting to HTML, Yodl splits
reports and books into files each holding a chapter. These can be
accessed through the table of contents. So, the document length can also be
relevant when you contemplate switching to a report or book.

Documents using special macros, must have defined these macros before they
are used. An appropriate location for these macros is immediately beyond the
preamble.  E.g., see the file Documentation/manual/manual.yo distributed
with the Yodl package.  This is the main file of this manual, showing the
preferred organization of Yodl files.

To answer yes-but-what-if oriented minds, here are two results of the 
wrong order of text, preamble and modifiers:
    
    o  If you put text before the preamble, i.e., before stating the
document type, chances are that Yodl happily translates the file, but
subsequent states probably fail. E.g., the <html> tag would come too
late in a HTML conversion, causing the HTML browser to become confused.  Or,
the \documentstyle definition would be seen too late by the LaTeX
typesetter.
    o  If you put modifiers, such as latexoptions, beyond the
document type, then these modifiers have no effect; though Yodl won't complain
either. The reason for this being that the definitions of such modifiers are
encountered only  after the stage where they were needed....


4.1.1: Document types

        As distributed, Yodl supports four document types: article, report,
book and the manual page. Note that document types are essentially
unrelated to output formats; a book can be converted to each of the output
formats, and a manual page can be converted to a .html file. Nevertheless,
some formats are particularly useful for some document types. A book
converted to the man output format to be processed later with groff
won't look too good. Its looks would greatly improve when the document would
be converted to ASCII using the ms output format.

Following the preamble and the definition of specialized macros symbols and
counters, documents start by specifying the document type.  The available
macros are:
    
    o  article(title)(author)(date): The article document type
should be used for short documents. Its arguments specify the document's
title, author and date.

In articles, the title page is numbered and the table of contents is on
the title page. The sectioning commands sect, subsect etc.  are
available.
    o  report(title)(author)(date): The report document type differs
from an article in that it has a separate unnumbered title page, a table
of contents on a page of its own, and it supports the sectioning command
chapter in addition to the ones supported by articles. A report
should be used fir larger documents.
    o  book(title)(author)(date): The book type is for even larger
documents. In addition to the sectioning commands supported by report it
supports the sectioning command part.
    o  plainhtml(title): This document type is typically used in HTML
output. It's implemented for situations where you only need to create a HTML
file, but want to use Yodl to help you by providing useful macros.  This
document type is similar to article, but does not require you to specify
author and date arguments (In fact, you can emulate plainhtml by
using an article, using empty author and date arguments).
    o  manpage(title)(section)(date)(source)(manual): The manpage
document type should only be used to write Unix-style manual pages. It uses
its own sectioning commands to reflect the necessary sections in a manual
page. This document format is described separately in 4.1.2.

These macros provide, globally, three functions: First, the macros
generate any commands that need to appear before `real' text is sent to the
output file.  E.g., the LaTeX output needs a \documentstyle
preamble, HTML output needs <html> and <body> tags.

Second, the macros define appropriate document-dependent settings. E.g., the
LaTeX converter defines the title, author and date using \title etc..

Third, the actual document is started. E.g., for LaTeX this means a
\begin{type}, followed by the appropriate commands to generate a
the document title and the table of contents.  The title setting in the
above macros defines the document title which always appears on the front page
of the document. For HTML output, this is also the title of the HTML file (or
files), as appearing in the HTML <title> tag.

The fact that the macros defining the document type perform many functions
means that once the macro is started, nothing `extra' can be inserted between,
e.g., the generated title and the table of contents. Sometimes this is not
what you'd like; as is the case with an abstract. Yodl therefore uses
modifiers, appearing before the document type macros, to insert
information between the various elements of a document definition.


4.1.2: The manpage document type

        The manpage document type was implemented to simplify the construction of
Unix-style manual pages. Yodl mapage documents can be converted to groff
documents (using yodl2man), to html documents (using yodl2html), or
to plain ascii text documents (using yodl2txt). 

A manpage document must be organized as follows:
    
    o  The manual page itself is defined, using the macro
        manpage(short title)
            (section)
            (date)
            (source)
            (manual)
        
    Its arguments are:
    
    o Short title: This should be the program name or something
similar; i.e., whatever the manpage is describing.
    o Section: A number, stating the manpage section. The Linux man (7)
page recognizes the following manpage sections:
        
        o   Section 1 is for commands, like ls;
        o  Section 2 is for system calls, like fork();
        o  Section 3 is for library calls, like strdup();
        o  Section 4 is for special files (like devices);
        o  Section 5 is for file formats, (like syslog.conf);
        o  Section 6 is for games;
        o  Section 7 is for macro packages and conventions;
        o  Section 8 is for system management commands;
        o  Section 9 is for other types of manpages, such as kernel
            commands.

o Date: The date of release.
    o Source: The package where the manpage belongs to.
    o Manual: The manual to which the package belongs.

The arguments of the manpage macro define, e.g., the headers and
footers of the manual page. The date, source and manual arguments
can be empty.
    1.  The subject of the manpage is defined using
        
    manpagename(name)(short description)
        
    The name argument should be a short name (e.g., the program name), and
the short description should state the function. The descriptive argument
is used by, e.g., the whatis database.
    2.  The synopsis starts after:
        
    manpagesynopsis()
        
    Following this, an abbreviated usage information is presented. This
information should show, e.g., the possible program flags and required
arguments; but no more.
    3.  The description is given after:
        
    manpagedescription()
        
    This is followed by some descriptive text. The descriptive text can
e.g. show what the program (function, file, game, etc.) is supposed to do.
    4.  Options are expected after:
        
    manpageoptions()
        
    The options are typically a descriptive list of possible flags and their
meaning. This section lists the information of the synopsis, but also gives an
in-depth description. The manpageoptions() section is optional.
    5.  Necessary files are listed after:
        
    manpagefiles()
        
    6.  The `see also' entry is defined by:
        
    manpageseealso()
        
    This is then followed by a list of related manual pages. Here, use the
format bf(topic)(sectionnr), e.g., Yodl(1).
    7.  Diagnostics are described after:
        
    manpagediagnostics()
        
    Diagnostics can state, e.g., what error messages are produced by the
program and what the cure is.
    8.  Known bugs should be mentioned after:
        
    manpagebugs()
        
    This section is optional.
    9.  Finally, the author is stated after:
        
    manpageauthor()
        
    
    The manpage document type requires you to follow the
above order of commands strictly and to state all the necessary sections (and
optionally, to state the not required sections but in their proper sequence).
Furthermore, sectioning commands that are available in other document types
(sect, subsect etc.) are not allowed in a manpage. You can
however insert other sections in the manual page with the macro
manpagesection. This macro takes one argument: the title of the extra
section. It is suggested that you type the section name in upper case, to
conform to the standard.

As an example, the manual page for the yodl program follows (the
actual manual page may differ):
        
    manpage(yodl)
           (1)
           (1996)
           (The Yodl Package)
           (Yet oneOther Document Language)

    manpagename(yodl)(main Yodl converter)
    
    manpagesynopsis()
    YODL [-DNAME] [-IDIR] [-oFILE] [-PCMD] [-pPASS] [-t] [-v] [-w] [-h]
    [-?]  inputfile [inputfile...]

    manpagedescription()
    This manual page describes the YODL program, the main converter of the
    Yodl package. This program is used by the bf(yodl2....) shell scripts,
    e.g., bf(yodl2tex) or bf(yodl2html).

    manpageoptions()
    description(
    dit(-DNAME) Defines symbol em(NAME).
    dit(-IDIR) Overrules the standard include directory (default 
em(/usr/local/lib/yodl)) with em(DIR).
    dit(-oFILE) Specifies em(FILE) as the output file (default is stdout).
    dit(-PCMD) `Preloads' command em(CMD), as if em(CMD) was the first line 
of the input.
    dit(-pPASS) Defines em(PASS) as the maximum number of `passes'; when this 
number is exceeded, YODL aborts.
    dit(-t) Enables tracing mode. Useful for debugging.
    dit(-v) Raises the verbosity mode. Useful for debugging.
    dit(-w) Enables warning. When enabled, YODL warns when it encounters
inconsistencies.
    dit(-h, -?) Shows usage information.
    dit(inputfile) File to process, use em(-) to instruct YODL to read 
from stdin.
    )

    manpagefiles()
    The YODL program requires no files, but `normal' usage of the Yodl package
requires macro files installed (usually in bf(/usr/local/share/yodl)). The
files in this directory are included by the converters bf(yodl2txt) etc..

    manpageseealso()
    bf(yodl2tex), bf(yodl2html), bf(yodl2man), etc..

    manpagediagnostics()
    Warnings and errors of YODL are too many to enumerate, but all errors
are printed to em(stderr) after which YODL exits with a non-zero
status.

    manpagebugs()
    There may be bugs in the YODL program, but that's not very likely.
More likely you'll encounter bugs or omissions in the macro package
itself.

    manpageauthor()
    Karel Kubat
        


4.2: Predefined macros

    This section describes all macros defined by default. Altering or removing
these macros may produce unexpected results when converting Yodl documents to
other formats. Furthermore, these macros often depend on macros or other
symbols defined for internal use.

Many predefined macros depend on symbols start with XX. Therefore, it is
strongly advised not to start any locally defined symbol with XX as doing
so, or undefining existing symbols starting with XX, may also produce
unexpected results.

Here are the default macros, alphabetically ordered:


    
4.2.1: abstract(text)


Defines an abstract for an article or report type of document. Abstracts are
not implemented for books or manpages. Must appear before starting the
document using the article or report macro.


    
4.2.2: addntosymbol(symbol)(n)(text)


Adds text n times to symbol. The value n may also be the name
of a defined counter (which is not modified).


    
4.2.3: affiliation(site)


Defines an affiliation, to appear in the document titlepage below the author
field. Must appear before starting the document with article,
report or book. The affiliation is only printed when the author field
is not empty. When converting to html the way the affiliation is displayed can
be tuned using CSS id selector specifications. The affiliation has
id="affiliation".


    
4.2.4: AfourEnlarged()


Enlarges the usable height of A4 paper by 2 cm.: the top margin is reduced by
2 cm. This macro should be called in the preamble. The macro is available only
for LaTeX conversions.

This macros is somewhat obsolete. Instead, using PageEnlarged is advised


    
4.2.5: appendix()


Starts appendices


    
4.2.6: article(title)(author)(date)


Starts an article. The top-level sectioning command is (n)sect. In HTML
conversions only one output file is written, while the way the headings are
displayed can be tuned using CSS id selector specifications: the title has
id="title", the author id="author", and the date id="date".
)


    
4.2.7: attrib(text)


In html, pushes text as an attribute for the next html tag supporting
attrib.  E.g, to set a blue color and 30 pixel left-hand side margin for a
section use
    
    attrib(style="color:blue;margin-left:30px;")\ 
    sect(Section name)
     
    This results in the html markup

    
    <h1 style="color:blue;margin-left:30px;">Section name</h1>
    
    This macro is only effective with html conversions. It is applied in a
stack-wise fashion: when multiple attrib calls are used, then the topmost
attrib-string is added to the first macro calling the 
attribinsert macro, with subsequent macros using subsequent elements on
the attrib-stack. 

Commonly used attributes are id="idname", expecting a #idname CSS
label in either internal or external CSS specifications, or style="spec"
(as shown in the example). 

Example: when using
    
    attrib(width = "100" height = "100")
    attrib(id = "#fig")
    figure(imgfile)(Caption)(IMG)
    
    then the #id attribute is applied to <figure>, and the width
and height attributes are applied to <img>, which html markup is
inserted by the figure macro.

The attrib macro is supported by the following predefined macros (between
parentheses the number of attribute strings that are inserted by these macros;
if only 1 attribute string is inserted no number is shown): 

bf cell cells center chapter code dashes dit em figure(3) file htmltag
itdesc lchapter link lref lsect lsubsect lsubsubsect nchapter npart nsect
nsubsect nsubsubsect paragraph part quote row sc sect strong subs subsect
subsubsect subsubsubsect sups tableatt tbl tac tc tnac tnc tr tt ttbegin url
verb verborg verbinclude.


    
4.2.8: attribclear()


Removes any existing contents from the attrib-stack. This macro is only
active when converting to html


    
4.2.9: attribinsert()


In html, if the attrib-stack is not empty, 
inserts the value on top of the attrib-stack and then pops the topmost value.
If the attrib-stack is empty, nothing happens.


    
4.2.10: bf(text)


Sets text in boldface.


    
4.2.11: bind(text)


Generate a binding character (non-breaking space) after text.


    
4.2.12: book(title)(author)(date)


Starts a book document. The top-level sectioning command is (n)chapter,
(n)part being optional. In HTML output files are created for each
chapter, while the way the headings are displayed can be tuned using
CSS id selector specifications: the title has id="title", the author
id="author", and the date id="date".
)


    
4.2.13: cell(contents)


Sets a table cell, i.e., one element in a row. With the man/ms converters
multiple blanks between cell() macro calls are merged into a single blank
character.

Instead of using cell in table, consider using tc in tbl.


    
4.2.14: cells(nColumns)(contents)


Set a table cell over nColumns columns. With LaTeX and xml the
information in the combined cells is centered. 

With man/ms conversions the cells() macro simply calls the cell()
macro, but here the setmanalign() macro can be used to determine the
alignment of multiple cells.

With html the macro attrib can be used, but when it contains a style
specification the macro's default style="text-align: center" is ignored
(but it can optionally be specified using the attrib macro).

Instead of using cells in table, consider using tnc in tbl.


    
4.2.15: cellsline(from)(count)


Sets a horizontal line starting at column number from over count
columns in a row. If from is less then the number of columns already added
to a row then it is ignored. This macro must be embedded in a row macro
defining a table row.  To put a line across the table's full width use
rowline. To set horizontal lines across columns 1
until 2 and columns 4 until 5 table of a table use:
        
    row(cellsline(1)(2)cellsline(4)(2))
        
 Combining cellsline and cell or cells calls in one row produces
undefined results.

Instead of using cellsline in table, consider using tline in
tbl.


    
4.2.16: center(text)


Centers text. Use nl() in the text to break lines.  In html the
attrib macro is not supported, but a division (div) with style
definition text-align: center is used. To center a table in html use
the tableatt macro. If a table or tableatt macro is used inside a
center macro then the contents of columns are column-wise centered.

Inside a center(...) context the counter XXcenter is unequal 0.


    
4.2.17: chapter(title)


Starts a new chapter in books or reports.


    
4.2.18: cindex()


Generate an index entry for LaTex() or texinfo 
c-indices. Its argument is the
index entry.  See also the [fptv]index macro.


    
4.2.19: cite(text)


Sets text as a citation or quotation


    
4.2.20: clearpage()


Starts a new page, when the output format permits. Under HTML a horizontal
line is drawn.


    
4.2.21: code(text)


Sets text in code font, and prevents it from being expanded.
For unbalanced parameter lists, use CHAR(40) to get
( and CHAR(41) to get ).


    
4.2.22: columnline(from)(through)


Sets a horizontal line over some columns in a row. Note that columnline
defines a row by itself, consisting of just a horizontal line spanning some of
its columns, rather than the table's full width, like rowline. The two
arguments represent column numbers. It is the responsibility of the author to
make sure that the from and through values are sensible. I.e., 
        
    1 <= from <= through <= ncolumns
        
To set a horizontal line in just one column select through equal to
from.

Note: this macro cannot be used if multiple lines must be set in one
row. In those cases the macros tline, tskip, and tendline should be
used. 

Instead of using columnline in table, consider using tline in
tbl.

4.2.23: dashes()

Inserts two dashes in teletype font, and prevents them from being
expanded.  

In html the attrib macro is recognized by the <code> tag that is used
to embed the two dashes.

4.2.24: def(macroname)(nrofargs)(redefinition)

Defines macroname as a macro, having nrofargs arguments, and
expanding to redefinition. This macro is a shorthand for
DEFINEMACRO.
 An error occurs when the macro is already defined. Use
redef() to unconditionally define or redefine a macro.

4.2.25: description(list)

Sets list as a description list. Use dit(item) to
indicate items in the list.

4.2.26: dit(itemname)

Starts an item named itemname in a description list. The list should be
used in description macros. With html conversions the
contents of a description item is separated from the item itself. The dit
macro only defines the item, and not the description itself. This macro sets
the item in bold-face (`strong' font). The macro itdesc, available since
Yodl 3.05, can be used to defines an item and its description, using its
suggested format (i.e., indenting the description relative to the item).

4.2.27: eit()

Indicates an item in an enumerated list. The eit macro should be used as
an argument in enumeration macros.

4.2.28: ellipsis()

Sets ellipsis (...).

4.2.29: em(text)

Sets text as emphasized, usually italics.

4.2.30: email(address)

In HTML, this macro sets the address in a 
locator. In other output formats, the address is sent to the output. The
email macro is a special case of url.

4.2.31: enumeration(list)

enumeration() starts an enumerated list. Use eit() in the list to 
indicate items in the list.

4.2.32: euro()

Sets the euro currency symbol in latex, html, (and possibly sgml and xml). In
all other conversions EUR which is the official textual abbreviation
(cf. http://ec.europa.eu/euro/entry.html) is written. Note that LaTeX
may require latexpackage()(eurosym).

4.2.33: evalsymbol(symbol)(expression)

Symbol symbol receives the value resulting from evaluating
expression. E.g., if sym is a defined symbol, then
        
    evalsymbol(sym)(SUBSTR(hello world)(3)(2))
        
    assigns the value lo to sym.


    
4.2.34: fig(label)


This macro is a shorthand for figure ref(label) and just makes the typing
shorter, as in see fig(schematic) for .. See getfigurestring() and
setfigurestring() for the figure text.


    
4.2.35: figure(file)(caption)(label)


Sets the picture in file as a figure in the current document, using the
descriptive text caption. The label is defined as a placeholder for
the figure number and can be used in a corresponding ref statement. Note
that the file must be the filename without extension: By default, Yodl
will supply .gif when in HTML mode, or .ps when in LaTeX mode. Figures
in other modes may not (yet) haven been implemented.

When converting to html, this macro uses three attribute-strings (if
available). The string pushed first using an attrib-call defines the
attributes for its <figcaption> html-markup; the string pushed next defines
the attributes for its <img> html-markup; the string pushed last defines
the attributes for its <figure> html-markup. The figure macro's html
output is organized like this:
    
    <figure -attrib-string pushed last (if any)>
        <img ... -attrib-string pushed last but one>
        <figcaption -attrib-string pushed 2nd to last>
            ...
        </figcaption>
    </figure>
    
Starting with Yodl 3.07.00 no alt="Figure # is shown here..." attribute is
defined anymore for the img markup: an alt-attribute can easily be
defined at the last attrib-call, using getfigurestring() to obtain
Figure or its language-specific translation, and
COUNTERVALUE(XXfigurecounter) to obtain the order-number of the figure
shown in the next figure-macro call.

4.2.36: file(text)

Sets text as filename, usually boldface.
 In html attrib macro applies to the  tag.

4.2.37: findex()

Generate an index entry for LaTex() or texinfo 
f-indices. Its argument is the
index entry.  See also the [cptv]index macro.

4.2.38: footnote(text)

Sets text as a footnote, or between parentheses when the output format
 does not allow footnotes.

4.2.39: gagmacrowarning(name name ...)

Prevents the yodl program from printing cannot expand possible user
macro. E.g., if you have in your document the file(s) are .. then you
might want to put before that: gagmacrowarning(file). Calls 
NOUSERMACRO.

4.2.40: getaffilstring()

Expands to the string that defines the name of Affiliation Information, by
default AFFILIATION INFORMATION. Can be redefined for national language
support by setaffilstring(). Currently, it is relevant only for txt.

4.2.41: getauthorstring()

Expands to the string that defines the name of Author Information, by
default AUTHOR INFORMATION. Can be redefined for national language
support by setauthorstring(). Currently, it is relevant only for txt.

4.2.42: getchapterstring()

Expands to the string that defines a `chapter' entry, by default Chapter.
Can be redefined for national language support by setchapterstring().

4.2.43: getdatestring()

Expands to the string that defines the name of Date Information, by
default DATE INFORMATION. Can be redefined for national language
support by setdatestring(). Currently, it is relevant only for txt.

4.2.44: getfigurestring()

Returns the string that defines a `figure' text, in captions or in the
fig() macro. The string can be redefined using the setfiguretext()
macro.

4.2.45: getpartstring()

Expands to the string that defines a `part' entry, by default Part. Can
be redefined for national language support by setpartstring().

4.2.46: gettitlestring()

Expands to the string that defines the name of Title Information, by
default TITLE INFORMATION. Can be redefined for national language
support by settitlestring(). Currently, it is relevant only for txt.

4.2.47: gettocstring()

Expands to the string that defines the name of the table of contents, by
default Table of Contents. Can be redefined for national language
support by settocstring().

4.2.48: htmlcommand(cmd)

Writes cmd to the output when converting to html. The cmd is not
further expanded by Yodl.

4.2.49: htmlheadfile(file)

Adds the contents of file to the head section of an HTML
document. The contents of file are not interpreted and should contain plain
html text. This option can be useful when large bodies of text, like the
contents of <script> sections, must be included into the head section of
html documents. This macro is only active in the preamble, should only
specified once, and is only interpreted for html conversions.

4.2.50: htmlheadopt(option)

Adds the literal text option to the current information in the head
section of an HTML document. Option may (or: should) contain plain html
text. A commonly occurring head option is link, defining, e.g., a style
sheet. Since that option is frequently used, it has received a dedicated
macro: htmlstylesheet. When large bodies of html-text must be added to
html documents the macro htmlheadfile should be used. This macro is only
active in the preamble and is only interpreted for html conversions.

4.2.51: htmlnewfile()

In HTML output, starts a new file. All other formats are not affected. Note
that you must take your own provisions to access the new file; say via links.
Also, it's safe to start a new file just befoore opening a new section, since
sections are accessible from the clickable table of contents. The HTML
converter normally only starts new files prior to a chapter definition.

4.2.52: htmlstyle(tag)(definition)

Adds a  element to the head section
of an HTML document.

 Use htmlstyle to specify one or more CSS definitions which are eventually
inserted at the ellipsis (...) in the generic style definition shown
above. E.g., (using #rrggbb to specify a color, where rr are two
hexadecimal digits specifying the color's red component, gg two
hexadecimal digits specifying the color's green component, and bb two
hexadecimal digits specifying the color's blue component)  specifying
    htmlstyle(body)(color: #rrggbb; background-color: #rrggbb)
    htmlstyle(h1)(color: blue; text-align: center)
    htmlstyle(h2)(color: green)
    
    results in the element
    <style type="text/css">
        body {color: #rrggbb; background-color: #rrggbb;}
        h1 {color: blue; text-align: center;} 
        h2 {color: green;}
    </style>
    
 The macros htmlheadopt and htmlstylesheet could also be used to put
information into the head-section of an HTML document, but htmlheadopt is
of a much more general nature, while htmlstylesheet refers to CSS elements
stored in an external file. The macro attrib can be used to define
inline styles.

The htmlstyle macro is only active in the preamble and is only
interpreted for html conversions.

 Refer to available CSS specifications (cf.,
http://www.w3schools.com/cssref/ for an overview of how CSS
specifications are used, and which CSS specifications are available).

By default the internal style specification

    figure {text-align: center;} img {vertical-align: center;}

 is used. If this is not appropriate, specify nohtmlimgstyle() in the
preamble. 

4.2.53: htmlstylesheet(url)

Adds a  element to the head
section of an HTML document, using url in its href field. The argument
url is not expanded, and should be plain HTML text, without surrounding
quotes. The macro htmlheadopt can also be used to put information in the
head-section of an HTML document, but htmlheadopt is of a much more
general nature.  This macro is only active in the preamble and is only
interpreted for html conversions.

4.2.54: htmltag(tagname)(start)

Sets tagname as a HTML tag, enclosed by < and >. When start
is zero, the tagname is prefixed with /. As not all html tags are
available through predefined Yodl-macros (there are too many of them, some are
used very infrequently, and you can easily define macros for the tags for
which Yodl doesn't offer predefined ones), the htmltag macro can be used
to handle your own set of macros. In html the attrib macro is
supported. E.g.,
    
attrib(title="World Health Organization")\
    htmltag(abbr)()WHO+htmltag(abbr)(0)

4.2.55: ifnewparagraph(truelist)(falselist)

The macro ifnewparagraph should be called from the PARAGRAPH macro,
if defined. It will insert truelist if a new paragraph is inserted,
otherwise falselist is inserted (e.g., following two consecutive calls of
PARAGRAPH). This macro can be used to prevent outputting multiple blank lines.

4.2.56: includefile(file)

Includes file. The default
extension .yo is supplied if necessary.

Since Yodl version 3.00.0 Yodl's default file inclusion behavior has
changed. The current working directory no longer remains fixed at the
directory in which Yodl is called, but is volatile, changing to the directory
in which a yodl-file is located. This has the advantage that Yodl's file
inclusion behavior now matches the way C's #include directive
operates. The originally implemented file inclusion behavior is used when 
Yodl's -L (--legacy-include) option is used.

4.2.57: includeverbatim(file)

Include file into the output.  No processing is done, file should
be in preformatted form, e.g.: whenhtml(includeverbatim(foo.html))

4.2.58: it()

Indicates an item in an itemized list. Items in it macros are
arguments of itemization macros.

4.2.59: itdesc(itemname)(contents)

Starts an item and its description in a description list. Its name is
itemname, the contents of the item is defined by contents. The
itemname is defined by using the dit macro. 

With html conversions the contents are surrounded by 
 and

 tags, resulting in contents which are indented relative to the
itemname. When the attrib macro is used it is applied to the itemname
(dt-tags). 

With other conversions the contents are quoted (as if using
quote(contents)).

4.2.60: itemization(list)

Sets list as an itemizationd list. Use it() to indicate items in the
list.

4.2.61: kindex()

Generate an index entry for LaTex() or texinfo k-indices. Its argument is the
index entry.  See also the [cfptv]vindex macro.

4.2.62: label(labelname)

Defines labelname as an anchor for a link
command, or to stand for the last numbering of a section or figure in a
ref command.

4.2.63: langle()

Character <

4.2.64: languagedutch()

Defines the Dutch-language specific headers. Active this macro via
setlanguage(dutch).

4.2.65: languageenglish()

Defines the English-language specific headers. Active this macro via
setlanguage(english).

4.2.66: languageportugese()

Defines the Portugese-language specific headers. Active this macro via
setlanguage(portugese).

4.2.67: LaTeX()

The LaTeX symbol.

4.2.68: latexaddlayout(arg)

This macro is provided to add Yodl-interpreted text to  your own LaTeX layout
commands. The command is terminated with an end-of-line.
See also the macro latexlayoutcmds()

4.2.69: latexcommand(cmd)

Writes cmd plus a white space to the output when converting to LaTeX. The
cmd is not further expanded by Yodl.

4.2.70: latexdocumentclass(class)

Forces the LaTeX
\documentclass{...} setting to class. Normally the class is
defined by the macros article, report or book.  This macro
is an escape route in case you need to specify your own document class
for LaTeX. This option is a modifier and must
appear before the article, report or book macros.

4.2.71: latexlayoutcmds(NOTRANSs)

This macro is provided in case you want to put your own LaTeX layout commands
into LaTeX output. The NOTRANSs are pasted right after the
\documentclass stanza. The default is, of course, no local LaTeX
commands. Note that this macro does not overrule my favorite LaTeX
layout. Use nosloppyhfuzz() and standardlayout() to disable my favorite
LaTeX layout.

4.2.72: latexoptions(options)

Set latex options: documentclass[options].  
This command must appear before the document type is
stated by article, report, etc..

4.2.73: latexpackage(options)(name)

Include latex package(s), a useful package is, e.g.,
epsf. This command must appear before the document type is
stated by article, report, etc..

4.2.74: lchapter(label)(title)

Starts a new chapter in books or reports, setting a label at the beginning
of the chapter.

4.2.75: letter(language)(date)(subject)(opening)(salutation)(author)

Starts a letter written in the indicated language. The date of the letter is
set to `date', the subject of the letter will be `subject'. The letter starts
with `opening'. It is based on the `letter.cls' document class definition.
The macro is available for LaTeX only. Preamble command suggestions:
    
    o  latexoptions(11pt)
    o  PageEnlarged(2cm)(4cm)(2cm)(4cm)
    o  letterreplyto(name)(address)(postalcode/city)
    o  letterfootitem(phone)(number), maybe e-mail too.
    o  letteradmin(yourdate)(yourref)
    o  letterto(addressitem). Use a separate letterto() macro call
            for each new line of the address.


    
4.2.76: letteraddenda(type)(value)


Adds an addendum at the end of a letter. `type' should be `bijlagen',
`cc' or `ps'.


    
4.2.77: letteradmin(yourdate)(yourref)


Puts `yourletterfrom' and `yourreference' elements in the letter. If left
empty, two dashes are inserted.


    
4.2.78: letterfootitem(name)(value)


Puts a footer at the bottom of letter-pages. Up to three will usually fit.
LaTeX only.


    
4.2.79: letterreplyto(name)(address)(zip city)


Defines the `reply to' address in LaTeX or txt-letters.


    
4.2.80: letterto(element)


Adds `element' as an additional line to the address in LaTeX letters.


    
4.2.81: link(description)(labelname)


In HTML output a clickable link with the text description is created
that points to the place where labelname is defined using the label
macro, and attrib macro applies to the <a> tag.  Using
link is similar to url, except that a hyperlink is set pointing to a
location in the same document. For output formats other than HTML, only the
description appears.


    
4.2.82: lref(description)(labelname)


This macro is a combination of the ref and link macros. In HTML
output a clickable link with the text description and the label value is
created that points to the place where labelname is defined using the
label macro, and attrib macro applies to the <a>
tag. For output formats other than HTML, only the description and the
label value appears.


    
4.2.83: lsect(label)(title)


Starts a new section, setting a label at the beginning of the section.
 In html attrib macro applies to the <h2> tag.


    
4.2.84: lsubsect(label)(title)


Starts a new subsection. Other sectioning commands are
subsubsect and subsubsubsect. A label is added just before the
subsection.
 In html attrib macro applies to the <h3> tag.


    
4.2.85: lsubsubsect(label)(title)


Starts a sub-subsection, a label is added just before the section
 In html attrib macro applies to the <h4> tag.


    
4.2.86: lsubsubsubsect(label)(title)


Starts a sub-sub-sub section. This level of sectioning is not numbered, in
contrast to `higher' sectionings. A label is added just before the
subsubsubection.


    
4.2.87: lurl(locator)


An url described by its Locator.  For small urls with readable addresses.


    
4.2.88: mailto(address)


Defines the default mailto address for HTML output. Must appear
before the document type is stated by article, report, etc..


    
4.2.89: makeindex()


Make index for latex.


    
4.2.90: mancommand(cmd)


Writes cmd to the output when converting to man. The cmd is not
further expanded by Yodl.


    
4.2.91: manpage(title)(section)(date)(source)(manual)


Starts a manual page document. The section argument must be a number,
stating to which section the manpage belongs to. Most often used are commands
(1), file formats (5) and macro packages (7). The sectioning commands in a
manpage are not (n)sect etc., but manpage...(). The first section
must be the manpagename, the last section must be the
manpageauthor. The standard manpage for section 1 contains the following
sections (in the given order): manpagename, manpagesynopsis,
manpagedescription, manpageoptions, manpagefiles,
manpageseealso, manpagediagnostics, manpagebugs,
manpageauthor. Optional extra sections can be added with
manpagesection. Standard manpageframes for several manpagesections
are provided in /usr/local/share/yodl/manframes. Yodl manual pages can be
converted to groff, html, or plain ascii text formats.


    
4.2.92: manpageauthor()


Starts the AUTHOR entry in a manpage document. Must be the last section
of a manpage.


    
4.2.93: manpagebugs()


Starts the BUGS entry in a manpage document.


    
4.2.94: manpagedescription()


Starts the DESCRIPTION entry in a manpage document.


    
4.2.95: manpagediagnostics()


Starts the DIAGNOSTICS entry in a manpage document.


    
4.2.96: manpagefiles()


Starts the FILES entry in a manpage document.


    
4.2.97: manpagename(name)(short description)


Starts the NAME entry in a manpage document. The short description is
used by, e.g., the whatis database.


    
4.2.98: manpageoptions()


Starts the OPTIONS entry in a manpage document.


    
4.2.99: manpagesection(SECTIONNAME)


Inserts a non-required section named SECTIONNAME in a manpage
document. This macro can be used to augment `standard' manual pages with extra
sections, e.g., EXAMPLES. Note that the name of the extra section should
appear in upper case, which is consistent with the normal typesetting of
manual pages.


    
4.2.100: manpageseealso()


Starts the SEE ALSO entry in a manpage document.


    
4.2.101: manpagesynopsis()


Starts the SYNOPSIS entry in a manpage document.


    
4.2.102: manttquoted(onOff)


With man-conversions arguments of tt macros are displayed as normal text. To
enhance their visibility arguments of tt macros may be quoted, in which case
they are surrounded by backtics and normal quotes. By default arguments of tt
macros are not quoted. Quotation is used after calling manttquoted(1), and
is suppressed after calling manttquoted(0). The macro is only active when
converting to man.


    
4.2.103: mbox()


Unbreakable box in LaTeX. Other formats may have different opitions on
our unbreakable boxex.


    
4.2.104: metaC(text)


Put a line comment in the output.


    
4.2.105: metaCOMMENT(text)


Write format-specific comment to the output.


    
4.2.106: mscommand(cmd)


Writes cmd to the output when converting to ms. The cmd is not
further expanded by Yodl.


    
4.2.107: nbsp(count)


Inserts count `non-breaking space' characters into the generated output;
i.e., the space character is not optimized away. If the argument list is empty
one non-breaking space is inserted.


    
4.2.108: nchapter(title)


Starts a chapter (in a book or report) without generating a
number before the title and without placing an entry for the chapter in
the table of contents. 
 In html attrib macro applies to the <h1> tag.


    
4.2.109: nemail(name)(address)


Named email.
A more consistent naming for url, lurl, email and nemail would be
nice.


    
4.2.110: nl()


Forces a newline; i.e., breaks the current line in two.


    
4.2.111: nodeprefix(text)


Prepend text to node names, e.g. nodeprefix(LilyPond) sect(Overview)
Currently used in texinfo descriptions only.


    
4.2.112: nodeprefix(text)


Prepend text to node names, e.g. nodeprefix(LilyPond) sect(Overview)
Currently used in texinfo descriptions only.


    
4.2.113: nodetext(text)


Use text as description for the next node, e.g. nodetext(The GNU Music Typesetter)chapter(LilyPond)
Currently used in texinfo descriptions only.


    
4.2.114: nohtmlfive()


Starting yodl 3.05 html-conversions by default use html5. This can be
suppressed (in favor of using html4) by calling this macro. This macro merely
suppresses writing the initial <!DOCTYPE html> to generated html
files; it is only active in the preamble and is only interpreted for
html conversions.


    
4.2.115: nohtmlimgstyle()


By default html-pages specify

    (<style type="text/css" img {vertical-align: bottom;}></style>)

 This macro suppresses this img CSS style specification. This macro is
only active in the preamble and is only interpreted for html conversions.

4.2.116: nop(text)

Expand to text, to avoid spaces before macros e.g.: a^2. Although
a+sups(2) should have the same effect.

4.2.117: nosloppyhfuzz()

By default, LaTeX output contains commands that cause it to shut up about
hboxes that are less than 4pt overfull. When nosloppyhfuzz() appears
before stating the document type, LaTeX complaints are `vanilla'.

4.2.118: notableofcontents()

Prevents the generation of a table of contents. This is default in, e.g.,
manpage and plainhtml documents. When present, this option must
appear before stating the document type with article, report
etc..

4.2.119: notitleclearpage()

Prevents the generation of a clearpage() instruction after the typesetting
of title information. This instruction is default in all non article
documents. When present, must appear before stating the document type with
article, book or report.

4.2.120: notocclearpage()

With the LaTeX converter, no clearpage() instruction is inserted
immediately beyond the document's table of contents. The clearpage()
instruction is default in all but the article document type. When present,
must appear before stating the document type with article, book or
report. With other converters than the LaTeX converter, it is ignored.

4.2.121: notransinclude(filename)

Reads filename and inserts it literally in the text
not subject to macro expansion or character translation.
No information is written either before or after the file's contents, not even
a newline.

4.2.122: noxlatin()

When used in the preamble, the LaTeX converter disables the inclusion of the
file xlatin1.tex. Normally this file gets included in the LateX output
files to ensure the conversion of high ASCII characters (like e) to
LaTeX-understandable codes. (The file xlatin1.tex comes with the Yodl
distribution.)

4.2.123: nparagraph(title)

Starts a non-numbered paragraph (duh, corresponds to subparagraph in latex).

4.2.124: npart(title)

Starts a part in a book document, but without numbering it and without
entering the title of the part in the table of contents.
 In html attrib macro applies to the <h1> tag.

4.2.125: nsect(title)

Starts a section, but does not generate a number before the title nor
an entry in the table of contents. Further sectioning commands are
nsubsect, nsubsubsect and nsubsubsubsect.
 In html attrib macro applies to the <h2> tag.

4.2.126: nsubsect(title)

Starts a non-numbered subsection.  In html the attrib macro applies to
the <h3> tag.

4.2.127: nsubsubsect(title)

Starts a non-numbered sub-sub section. 
  In html attrib macro applies to the 
 tag.

4.2.128: nsubsubsect(title)

Starts a non-numbered sub-subsection.

4.2.129: PageEnlarged(up)(height)(left)(width)

Enlarges the usable width and height of printed pages: the first line printed
on paper is moved up by up units, the usable paper height is enlarged by
height units, the left margin is moved to the left by left units, and
the usable paper width is enlarged by width units.  E.g., A4 pages are by
default using relatively small text blocks. Instead the pages can be used more
efficiently by specifying PageEnlarged(2cm)(4cm)(2cm)(4cm).

This macro should be called in the preamble. The macro is available only
for LaTeX conversions.

4.2.130: paragraph(title)

Starts a paragraph. This level of sectioning is not numbered, in
contrast to `higher' sectionings (duh, corresponds to subparagraph in latex).
  In html attrib macro applies to the 
 tag.

4.2.131: part(title)

Starts a new part in a book document.
 In html attrib macro applies to the <h1> tag.

4.2.132: pindex()

Generate an index entry for LaTex() or texinfo 
p-indices. Its argument is the
index entry.  See also the [cftv]index macro.

4.2.133: plainhtml(title)

Starts a document for only a plain HTML conversion. Not available in
other output formats. Similar to article, except that an author- and
date field are not needed.

4.2.134: printindex()

Make index for texinfo (?).

4.2.135: quote(text)

Sets the text as a quotation. Usually, the text is indented, depending on
the output format. In html the attrib macro is recognized by the
<blockquote> tag.

4.2.136: rangle()

Inserts the right angle character (>).

4.2.137: redef(macro)(nrofargs)(redefinition)

Defines macro macro to expand to redefinition.
Similar to def, but any pre-existing definition is overruled. Use
ARGx in the redefinition part to indicate where the arguments should
be pasted. E.g., ARG1 places the first argument, ARG2 the second
argument, etc...

4.2.138: redefinemacro(macro)(nrofargs)(redefinition)

Defines macro macro to expand to redefinition.
Similar to def, but any pre-existing definition is overruled. Use
ARGx in the redefinition part to indicate where the arguments should
be pasted. E.g., ARG1 places the first argument, ARG2 the second
argument, etc... This commands is actually calling redef().

4.2.139: ref(labelname)

Sets the reference for labelname. Use label to define a label.

4.2.140: report(title)(author)(date)

Starts a report type document. The top-level sectioning command in a report
is chapter. In html the way the headings are displayed can be tuned using
CSS id selector specifications: the title has id="title", the author
id="author", and the date id="date".

4.2.141: roffcmd(dotcmd)(sameline)(secondline)(thirdline)

Sets a t/nroff command that starts with a dot, on its own line. The
arguments are: dotcmd - the command itself, e.g., .IP; sameline -
when not empty, sameline is set on the same line, following the
dotcmd; secondline - when not empty, is set on the next line;
thirdline - when not empty, is set on the third line. Note: dotcmd and
thirdline are not further expanded by Yodl, the other arguments are.

4.2.142: row(contents)

The argument contents may contain a man-page alignment specification
(only one specification can be entered per row), using setmanalign(). If
omitted, the standard alignment is used. Furthermore it contains the contents
of the elements of the row, using cell() or cells() macros. If
cells() is used, setmanalign() should have been used too. In this
macro call only the cell(), cells() and setmanalign() macros
should be called. Any other macro call may produce unexpected results.

The row macro defines a counter XXcol that can be inspected and is
incremented by predefined macros adding columns to a row. The counter is
initially 0. Predefined macros adding columns to a row add the number of
columns they add to the row inserting the contents of those columns.  These
macros rely on the correct value of this counter and any user-defined macros
adding columns to table rows should correctly update XXcol.
 In html attrib macro applies to the <tr> tag.

Instead of using row in table, consider using tr in tbl.

4.2.143: rowline()

Sets a horizontal line over the full width of the table. See also
the columnline macro. Use rowline instead of a row macro call to
provide a table with a horizontal line-separator.

Instead of using rowline consider using tline in a tbl argument.

4.2.144: sc(text)

Set text in the tt (code) font, using small caps.
 In html the attrib macro is not supported, while the code
section is embedded in a 
 section.

4.2.145: sect(title)

Starts a new section. In html the attrib macro is recognized by the
<h2> tag.

4.2.146: setaffilstring(name)

Defines name as the `affiliation information' string, by default
AFFILIATION INFORMATION. E.g., after setaffilstring(AFILIACION),
Yodl outputs this Spanish string to describe the affiliation information.
Currently, it is relevant only for txt.

4.2.147: setauthorstring(name)

Defines name as the `Author information' string, by default
AUTHOR INFORMATION. E.g., after setauthorstring(AUTOR),
Yodl outputs this portuguese string to describe the author information.
Currently, it is relevant only for txt.

4.2.148: setchapterstring(name)

Defines name as the `chapter' string, by default Chapter. E.g., after
setchapterstring(Hoofdstuk), Yodl gains some measure of national language
support for Dutch. Note that LaTeX support has its own NLS, this macro doesn't
affect the way LaTeX output looks.

4.2.149: setdatestring(name)

Defines name as the `date information' string, by default
DATE INFORMATION. E.g., after setdatestring(DATA),
Yodl outputs this portuguese string to describe the date information.
Currently, it is relevant only for txt.

4.2.150: setfigureext(name)

Defines the name as the `figure' extension. The extension should include
the period, if used. E.g., use setfigureext(.ps) if the extensions
of the figure-images should end in .ps

4.2.151: setfigurestring(name)

Defines the name as the `figure' text, used e.g. in figure captions. E.g.,
after setfigurestring(Figuur), Yodl uses Dutch names for figures.

4.2.152: sethtmlfigureext(ext)

Defines the filename extension for HTML figures, defaults to .jpg. Note
that a leading dot must be included in ext. The new extension takes effect
starting with the following usage of the figure macro.  It is only active
in html, but otherwise acts identically as setfigureext().

See also the setlatexfigureext macro.

4.2.153: htmlmetacharset(meta-charset)

Adds  to the head of html documents. By
default  is used. This macro is only active in the
preamble and is only interpreted for html conversions.

4.2.154: setincludepath(name)

Sets a new value of the include-path specification used when opening .yo
files. A warning is issued when the path specification does not include a .:
element. Note that the local directory may still be an element of the new
include path, as the local directory may be the only or the last element of
the specification. For these eventualities the new path specification is not
checked.

4.2.155: setlanguage(name)

Installs the headers specific to a language. The argument must be the name of
a language, whose headers have been set by a corresponding
languageXXX() call. For example: languagedutch(). The
language macros should set the names of the headers of the following elements:
table of contents, affiliation, author, chapter, date, figure, part and title

4.2.156: setlatexalign(alignment)

This macro defines the table alignment used when setting tables in LaTeX.
Use as many l (for left-alignment), r (for right alignment), and c
(for centered-alignment) characters as there are columns in the table. See
also table().

Instead of using the table macro consider using the tbl macro.

4.2.157: setlatexfigureext(ext)

Defines the filename extension for encapsulated PostScript figures in LaTeX,
defaults to .ps. The dot must be included in t new extension ext. The
new extension takes effect starting with a following usage of the figure
macro. It is only active in LaTeX, but otherwise acts identically as
setfigureext().

See also the sethtmlfigureext macro.

4.2.158: setlatexverbchar(char)

Set the char used to quote LaTeX 
\verb
 sequences

4.2.159: setmanalign(alignment)

This macro defines the table alignment in the context of the table
macro, and is used when setting tables in man-pages (see tbl(1)).

Use as many l (for left-alignment), r (for right alignment), and c
(for centered-alignment) characters as there are columns in the
table. 

Use s to indicate that the column to its left is combined (spans into) the
current column. Use this specification when cells spanning multiple columns
must be defined. 

Each row in a table which must be convertible to a manpage may be preceded by
its own setmanalign call.  

Note that neither rowline nor columnline requires setmanalign
specifications, as these macros define rows by themselves. It is the
responsibility of the author to ensure that the number of alignment characters
is equal to the number of columns of the table.

Instead of using the table macro consider using the tbl macro.

4.2.160: setpartstring(name)

Defines name as the `part' string, by default Part. E.g., after
setpartstring(Teil), Yodl identifies parts in the German way. Note that
LaTeX output does its own national language support; this macro doesn't affect
the way LaTeX output looks.

4.2.161: setrofftab(x)

Sets the character separating items in a line of input data of a roff
(manpage) table. By default it is set to ~. This separator is used
internally, and needs only be changed (into some unique character) if the
table elements themselves contain ~ characters.

This macro can be used in the context of the table and tbl macros.

4.2.162: setrofftableoptions(optionlist)

Set options used for man-conversion, as used by the tbl and table
macros. By default no options are used. Multiple options should be separated
by blanks. From the tbl(1) manpage, the following options are available:
    
    o  center Centers the table; default is left-justified. In the
        context of the tbl macro this is implied when the tbl macro is
        specified as argument of the center macro.
    o  expand Makes the table as wide as the current line length
    o  box Encloses the table in a box
    o  allbox Encloses each item of the table in a box

See also setrofftab which is used to set the character separating
    items in a line of input data. 

4.2.163: settitlestring(name)

Defines name as the `title information' string, by default
TITLE INFORMATION. E.g., after settitlestring(TITEL),
Yodl outputs this Dutch string to describe the title information.
Currently, it is relevant only for txt.

4.2.164: settocstring(name)

Defines name as the `table of contents' string, by default Table of
Contents. E.g., after settocstring(Inhalt), Yodl identifies the table
of contents in the German way. Note that LaTeX output does its own national
language support; this macro doesn't affect the way LaTeX output looks.

4.2.165: sgmlcommand(cmd)

Writes cmd to the output when converting to sgml. The cmd is not
further expanded by Yodl.

4.2.166: sgmltag(tag)(onoff)

Similar to htmltag, but used in the SGML converter.

4.2.167: sloppyhfuzz(points)

By default, LaTeX output contains commands that cause it to shut up about
hboxes that are less than 4pt overfull. When sloppyhfuzz() appears
before stating the document type, LaTeX complaints occur only if hboxes are
overfull by more than points.

4.2.168: standardlayout()

Enables the default LaTeX layout. When this macro is absent, then the
first lines of paragraphs are not indented and the space between
paragraphs is somewhat larger. The standardlayout() directive must appear
before stating the document type as article, report, etc..

4.2.169: strong(contents)

In html and xml the contents are set between  and
 tags. 
 In html attrib macro applies to the  tag.

4.2.170: subs(text)

Sets text in subscript in supporting formats.  
 In html the attrib macro is recognized by the <sub> tag.

For superscripting, the sups macro can be used.

4.2.171: subsect(title)

Starts a new subsection. Other sectioning commands are
subsubsect and subsubsubsect.
 In html attrib macro applies to the <h3> tag.

4.2.172: subsubsect(title)

Starts a sub-subsection.
 In html attrib macro applies to the <h4> tag.

4.2.173: subsubsubsect(title)

Starts a sub-sub-sub-subsection. This level of sectioning is not numbered, in
contrast to `higher' sectionings.

4.2.174: sups(text)

Sets text in superscript in supporting formats
 In html the attrib macro is recognized by the <sup> tag.

For subscripting, the subs macro can be used.

4.2.175: table(nColumns)(alignment)(Contents)

Instead of using the table macro, consider using the tbl macro.

The table()-macro defines a table. Its first argument specifies the number
of columns in the table.

Its second argument specifies the (standard) alignment of the information
within the cells as used by LaTeX or man/ms. Use l for left-alignment,
c for centered-alignment and r for right alignment.

Its third argument defines the contents of the table which are the rows, each
containing column-specifications and optionally man/ms alignment definitions
for this row.

See also the tableatt macro and the specialized setmanalign() macro.

4.2.176: tableatt(nColumns)(alignment)(Contents)

Instead of using the tableatt macro, consider using the tbl macro.

The tableatt()-macro defines a table. The last attrib call that was
specified before using the tableatt()-macro is used to specify html
attributes for the table. E.g., to center a table in html use
        
    attrib(style="margin-left:auto;margin-right:auto;")
    tableatt(...)
        
    The macro's first argument specifies the number of columns in the table.
Its second argument specifies the (standard) alignment of the information
within the cells as used by LaTeX or man/ms. Use l for left-alignment,
c for centered-alignment and r for right alignment. Its third argument
defines the contents of the table which are the rows, each containing
column-specifications and optionally man/ms alignment definitions for this
row.

See also the table macro and the specialized setmanalign() macro.


    
4.2.177: tac(alignment)(contents)


This macro is one of the four macros that can be used to define column
contents of rows of tables defined by the tbl macro. Alternatively, tc,
tnc, and tnac can be used.

The tac macro is used as argument of the tr macro. The cell's
alignment is defined by the alignment specification, containing at most
two alignment specifications: a horizontal alignment (one of c, l, r
(centered, left-aligned, right-aligned)) and a vertical alignment (one of t, b
(vertical top- and bottom-alignment)) (not all conversion types may support
all alignment types, e.g., man-conversion does not support vertical bottom
alignment). Specifications other than c, l, r, b, and t and specifications
beyond the second one are ignored. The result of specifying conflicting
alignment types (e.g., lr or tb) is not defined.

When converting to man, if the table's contents should span multiple rows,
then a groff/troff(1) text block must be used. Since most tables do
not use this, a text block is not generated by default. To actually wrap the
contents of column elements in a text block while converting to man prefix
the first text block requiring a text-block wrapping by twrap(1), and end
the last text block requiring a text-block wrapping by wrap(0).

The tao macro can be used to overrule the specified alignment for a
specific conversion type.

The macro tac recognizes attrib.


    
4.2.178: tao(type)(specification)


This macro is used inside the tbl macro to override the alignment
specification that would otherwise be used for the next table element. It is
only active for the next tc, tnc, tac, or tnac call. Its first
argument defines the conversion type for which the override should be used,
its second argument defines the alignment specification to use.

Here are some examples:
        
tbl(lr)(
    tr(
        tc(left aligned)
        tc(right aligned)
    )
    tr(
        tao(html)(c)
          tc(left aligned, centered with html)
        tao(latex)(l)
        tao(man)(l)
          tac(c)(centered, latex and man: left aligned)
    )
)
        

Further details about the tao macro are provided in the yodltables(7)
man-page.


    
4.2.179: tbl(align)(contents)


The tbl macro refines the more basic table macro. It was named after
the tbl(1) table formatting program used with troff(1) documents.

The tbl macro currently is available for html, man/ms, latex and
txt conversions.

Its first argument defines the alignment of the information in the table's
columns, and is used by all conversions except txt. Use l for
left-alignment, c for centered-alignment and r for
right-alignment. Individual cells of the table may override these default
settings using the macros tac and tnac.

Its second argument defines the contents of the table consisting of rows
(using tr), and horizontal lines (using tline), which may extend over
the full table width or may cover one or more individual columns. With txt
conversion rough approximations of horizontal lines are used.

Tables defined by the tbl macro are centered (pseudo centering (8 space
characters) is used for txt conversion) when used as argument of the
center macro.

See also the tao macro for information about how to realize specific
alignments for specific conversion types.

When defining tbl tables it is advised to clearly layout the table
specification. To avoid inadvertently introducing new lines lines should end
in a backslash (or 
The macro tbl recognizes attrib. 


    
4.2.180: tc(contents)


This macro is one of the four macros that can be used to define column
contents of rows of tables defined by the tbl macro. Alternatively,
tnc, tac, and tnac can be used.

The tc macro is used as argument of the tr macro. Its order within a
row defines its type attribute, using the alignment specification defined by
the first argument of the tbl call. E.g., if tbl(clr)(...) was used,
then the contents of the first tc call in a tr is centered in the
table's first column; the contents of the second tc call is left-aligned
in the table's second column; and the contents of the third tc call is
right-aligned in the table's third column.

When converting to man, if the table's contents should span multiple rows,
then a groff/troff(1) text block must be used. Since most tables do
not use this, a text block is not generated by default. To actually wrap the
contents of column elements in a text block while converting to man prefix
the first text block requiring a text-block wrapping by twrap(1), and end
the last text block requiring a text-block wrapping by wrap(0).

The tao macro can be used to overrule the default alignment specification 
for a specific conversion type.

The macro tc recognizes attrib. 


    
4.2.181: tcell(text)


Roff helper to set a table text-cell, i.e., a paragraph.  For LaTeX
special table formatting p{} should be used.

When using the tbl macro for defining tables the twrap macro can be
used to set table elements in text-blocks (i.e., enclosing text, possibly
containing newlines in T{ and T} sequences).


    
4.2.182: telycommand(cmd)


Writes cmd to the output when converting to tely. The cmd is not
further expanded by Yodl.


    
4.2.183: TeX()


The TeX symbol.


    
4.2.184: texinfocommand(cmd)


Writes cmd to the output when converting to texinfo. The cmd is not
further expanded by Yodl.


    
4.2.185: tindex()


Generate an index entry for LaTex() or texinfo 
t-indices. Its argument is the
index entry.  See also the [cfpv]index macro.


    
4.2.186: titleclearpage()


Forces a new page (using clearpage) following the title of a
document. This is already the default in books and reports, but can be
overruled using notitleclearpage. When present, it must appear in the
preamble, i.e., before the document type is stated as article, book or
report.


    
4.2.187: tline(beginNr)(endNr)


This macro is used to insert a horizontal line spanning one or more columns
of a table defined by the tbl macro.

If endNr is not specified, and the tline call does not follow a
previous line call in which endNr was specified, then a horizontal
line spanning the full width of the table is defined (except when converting
to plain text in which case a line of beginNr - (minus) characters is
written; if beginNr is not specified then a line of 60 - characters is
written).

If endNr is not specified, but the tline call follows previous tline
calls that did specify endNr then the current row is ended. 

If endNr is specified, then a horizontal line is set, starting at column
number beginNr continuing through column number endNr. Note that these
are numbers, not offsets: beginNr should be at least 1, endNr
must at least be equal to beginNr and should be at most equal to the
number of columns in the table. The beginNr values of subsequent tline
calls refer to the same row as the first tline call, and must exceed
endNr of the previous tline call.

Examples:
        
    tline()()       sets a line spanning the full table width
    tline(1)(1)     sets a line in column 1
    tline(3)(4)     sets another line in column 3 and 4
    tline()()       ends the previous line
    tline()()       sets a line spanning the full table width
        


    
4.2.188: tnac(nCells)(alignment)(contents)


This macro is one of the four macros that can be used to define column
contents of rows of tables defined by the tbl macro. Alternatively, tc,
tac, and tnc can be used.

The tnac macro is used as argument of the tr macro. Its first argument
defines the number of columns spanned by the contents (2nd argument) 
of the tnc macro. 

The cell's alignment is defined by the macro's second (alignment)
specification, containing at most two alignment specifications: a horizontal
alignment (one of c, l, r (centered, left-aligned, right-aligned)) and a
vertical alignment (one of t, b (vertical top- and bottom-alignment)) (not all
conversion types may support all alignment types). Specifications other than
c, l, r, b, and t and specifications beyond the second one are ignored. The
result of specifying conflicting alignment types (e.g., lr or tb) is
not defined.

When converting to man, if the table's contents should span multiple rows,
then a groff/troff(1) text block must be used. Since most tables do
not use this, a text block is not generated by default. To actually wrap the
contents of column elements in a text block while converting to man prefix
the first text block requiring a text-block wrapping by twrap(1), and end
the last text block requiring a text-block wrapping by wrap(0).  Multiple
rows in a text block are top-aligned with left and righ neighboring cells.

The tao macro can be used to overrule the default alignment specification 
for a specific conversion type.

The macro tnac recognizes attrib.


    
4.2.189: tnc(nCells)(contents)


This macro is one of the four macros that can be used to define the column
contents of rows of tables that are defined by the tbl
macro. Alternatively, tc, tac, and tnac can be used.

The tnc macro is used as argument to the tr macro. Its first argument
defines the number of columns spanned by the contents (2nd argument) 
of the tnc macro. The contents are centered in the nCells columns.

When converting to man, if the table's contents should span multiple rows,
then a groff/troff(1) text block must be used. Since most tables do
not use this, a text block is not generated by default. To actually wrap the
contents of column elements in a text block while converting to man prefix
the first text block requiring a text-block wrapping by twrap(1), and end
the last text block requiring a text-block wrapping by wrap(0).  Multiple
rows in a text block are top-aligned with left and righ neighboring cells.

The tao macro can be used to overrule the default alignment specification 
for a specific conversion type.

The macro tc recognizes attrib. 


    
4.2.190: tocclearpage()


With the LaTeX converter, a clearpage() directive if inserted,
immediately following the document's table of contents. This is already the
default in all but the article document type, but it can be overruled by
notocclearpage(). When present, it must appear in the preamble; i.e.,
before the document type is stated with article, book or
report. With other converters than the LaTeX converter, it is ignored.


    
4.2.191: tr(contents)


This macro defines the rows of a table that is defined by the tbl macro.

The macro tr expects one argument: the contents of the row, defining the
row's column elements. It is not used for defining a (partial) horizontal
line: to set horizontal lines in a table defined by the tbl macro use the
macro tline.

Normally the contents of the columns in a (tr) row is defined by 
of one or more calls to the macros tc, tac, tnc, and/or tnac.

The macro tr recognizes attrib.


    
4.2.192: tt(text)


Sets text in teletype font, and prevents it from being expanded.
When converting to man, text is surrounded by a backtick and a single
quote character.

For unbalanced parameter lists, use CHAR(40) to get
( and CHAR(41) to get ).

The tt macro does interpret character tables as well as any SUBST
definitions. This is usually what is intended. In situations where this is
unwelcome the ttbegin and ttend pair of macros can be used, between
which the builtin commands PUSHSUBST, POPSUBST, NOEXPAND and/or
NOTRANS can be used. E.g., to clearly show two hyphens in LaTeX 
teletype font use 
    
    ttbegin()--ttend()
    
rather than
    
    tt(--)
    
    Likewise, use ttbegin and ttend if the teletype text contains
accented letters like e. To set this in teletype font use 
ttbegin()\"e+ttend().

With html conversions the attrib macro applies to the <code> tag.

With man conversions the arguments of tt macros can be quoted. See the
manttquoted macro for details.


    
4.2.193: ttbegin()


Initiates text set in teletype font. Following the text to set in
teletype font a ttend() macro should be called.

Usually the tt macro can be used instead of the ttbegin --
ttend combination. However, tt interprets character tables as well as
SUBST definitions. In situations where this is unwelcome the ttbegin
and ttend pair of macros can be used, between which builtin commands like
PUSHSUBST, POPSUBST, NOEXPAND and/or NOTRANS can be used.

In html the attrib macro applies to the <code> tag.


    
4.2.194: ttend()


Ends text set in teletype font following ttbegin. Refer to the
ttbegin macro's description for details.


    
4.2.195: twrap(value)


Used for man/ms conversions only: when called with a non-zero argument
before using the tc, tnc, tac, and tnac macros then their contents are
wrapped in text blocks (T{ ... T} blocks). To end the wrapping
twrap(0) must be called. E.g., in the following row-definition the
contents of columns three and four are set in T-blocks when converting to
man/ms:
        
    tr(tc(one)tc(two)twrap(1)tc(one)tc(two)twrap(0))


    
4.2.196: txtcommand(cmd)


Writes cmd to the output when converting to txt. The cmd is not
further expanded by Yodl.


    
4.2.197: url(description)(locator)


In LaTeX documents the description is sent to the output. For HTML,
a link is created with the descriptive text description and pointing
to locator. The locator should be the full URL, including
service; e.g, http://www.icce.rug.nl, but excluding the double
quotes that are necessary in plain HTML. Use the macro link to create
links within the same document. For other formats, something like
description [locator] will appear.
 In html attrib macro applies to the <a> tag.


    
4.2.198: verb(text)


Sets text in verbatim mode: not subject to macro expansion or character
table expansion, and starting with Yodl version 4.00.00: not using SUBST
definitions. See also verborg, which does not provide the protection
against SUBST definitions.

While converting Yodl-documents to target document types Yodl frequently uses
the (not further documented) builtin function XXSUBST. In the
unlikely event that the text XXSUBST(...) must be written
in a document, the sequence
    
    XXSUBST+CHAR(40)...CHAR(41)
    
    can be used.

The text that is passed as argument to the verb-macro appears literally
on the output, usually in a teletype font (that depends on the output
format). This macro is for larger chunks, e.g., listings. 

When starting the verb( macro on a line by itself and writing the
closing parenthesis on a line by itself then those newlines also appear in the
resulting verbatim text. To omit those lines immediately start the first line
of text after verb and append the closing parenthesis to the last line of
verbatim text. E.g.,
    verb(    First line of indented literal text
    Last line of indented literal text)

When unbalanced parameter lists are required, use CHAR(40) to get
( and CHAR(41) to get ).


    
4.2.199: verbinclude(filename)


Reads filename and inserts it literally in the text, set in verbatim mode.
not subject to macro expansion. The text appears literally on the output,
usually in a teletype font (that depends on the output format). This macro is
an alternative to verb(...), when the text to set in verbatim mode is
better kept in a separate file.


    
4.2.200: verbinsert(args)


Passes args to yodlverbinsert(1), inserting its output into the
converted file. This macro can be used to insert, e.g., a line-numbered
indented file, or a labeled subsection of a file, into the file that's
currently being written by yodl. E.g,
    
verbinsert(-ans4 file)       -- inserts file, showing line
                                numbers, using a 4 blank-space
                                character wide indentation.

verbinsert(-ns4 //SECT file) -- inserts the section of file, 
                                labeled //SECT file, showing 
                                line numbers, using a 4 
                                blank-space character wide 
                                indentation.
    


    
4.2.201: verborg(text)


Sets text in verbatim mode: not subject to macro expansion or character
table expansion, and starting with Yodl version 4.00.00: this macro replaces
the previously defined verb macro. The current verb macro surrounds
this macro by PUSHSUBST and POPSUBST.

The text that is passed as argument to the verborg-macro appears
literally on the output, albeit that SUBST definitions are processed,
usually in a teletype font (that depends on the
output format). This macro is for larger chunks, e.g., listings.

When unbalanced parameter lists are required, use CHAR(40) to get
( and CHAR(41) to get ).


    
4.2.202: verbpipe(command)(text)


Pipe text through command, but don't expand the output.


    
4.2.203: vindex()


Generate an index entry for LaTex() or texinfo v-indices. 
Its argument is the index entry. 
See also the [cfkpt]index macro.


    
4.2.204: whenhtml(text)


Sends text to the output when in HTML conversion mode. The text is
further expanded if necessary.


    
4.2.205: whenlatex(text)


Sends text to the output when in LATEX conversion mode. The text is
further expanded if necessary.


    
4.2.206: whenman(text)


Sends text to the output when in MAN conversion mode. The text is
further expanded if necessary.


    
4.2.207: whenms(text)


Sends text to the output when in MS conversion mode. The text is
further expanded if necessary.


    
4.2.208: whensgml(text)


Sends text to the output when in SGML conversion mode. The text is
further expanded if necessary.


    
4.2.209: whentely(text)


Sends text to the output when in TELY conversion mode. The text is
further expanded if necessary.


    
4.2.210: whentexinfo(text)


Sends text to the output when in TEXINFO conversion mode. The text is
further expanded if necessary.


    
4.2.211: whentxt(text)


Sends text to the output when in TXT conversion mode. The text is
further expanded if necessary.


    
4.2.212: whenxml(text)


Sends text to the output when in XML conversion mode. The text is
further expanded if necessary.


    
4.2.213: xit(itemname)


Starts an xml menu item where the file to
which the menu refers to is the argument of the xit() macro. It
should be used as argument to xmlmenu(), which has a 3rd argument:
the default path prefixed to the xit() elements. 

This macro is only available
within the xml-conversion mode. The argument must be a full filename,
including .xml extension, if applicable.

No .xml extension indicates a subdirectory, containing another sub-menu.


    
4.2.214: xmlcommand(cmd)


Writes cmd to the output when converting to xml. The cmd is not
further expanded by Yodl.


    
4.2.215: xmlmenu(order)(title)(menulist)


Starts an xmlmenu. Use itemization() to define the items. Only
available in xml conversion. The menutitle appears in the menu as the heading
of the menu.  The menulist is a series of xit() elements, containing
the name of the file to which the menu refers as their argument (including a
final /).  Prefixed to evert every xit()-element is the value of
XXdocumentbase.

Order is the the `order' of the menu. If omitted, no order is defined.


    
4.2.216: xmlnewfile()


In XML output, starts a new file. All other formats are not affected. Note
that you must take your own provisions to access the new file; say via links.
Also, it's safe to start a new file just befoore opening a new section, since
sections are accessible from the clickable table of contents. The XML
converter normally only starts new files prior to a chapter definition.


    
4.2.217: xmlsetdocumentbase(name)


Defines name as the XML document base. No default.
Only interpreted with xml conversions. It is used with the figure and xmlmenu
macros.


    
4.2.218: xmltag(tag)(onoff)


Similar to htmltag, but used in the XML converter.


4.3: Conversion-related topics



4.3.1: Conversion-type specific literal commands

        According to the format of the output file, the macro package defines a given 
symbol: 
    
    o  latex when the output format is LaTeX,
    o  html when the output format is HTML,
    o  man when the output format is groff in conjunction with the
man macro package,
    o  ms when the output format is groff with the ms package,
    o  sgml when the output format is SGML,
    o  txt when the output format is plain ASCII.
    o  xml when the output format is XML.

The defined symbol can be tested in a document to determine the conversion
type.

Furthermore, the package defines the following macros to send literal text 
(commands in the output format) to the output file:
    
    o  latexcommand(cmd): sends the LaTeX command cmd when in LaTeX
conversion mode. The cmd is not further expanded.
    o  htmlcommand(cmd): sends the HTML command cmd when in HTML 
conversion mode.  The cmd is not further expanded.
    o  htmltag(tag)(onoff): sends <tag> to the output when onoff
is nonzero, or sends </tag> when onoff is zero. Only active in
HTML conversions.
    o  mancommand(cmd): sends cmd to the output when in man 
conversion mode.  The cmd is not further expanded.
    o  mscommand(cmd): sends cmd to the output when in ms
conversion mode. The cmd is not further expanded.
    o  roffcmd(dotcmd)(trailer)(secondline)(thirdline): sends a command
to the output when in man or ms conversion mode. The dotcmd is the
typical groff command that starts with a dot. All other arguments may be
empty, but when given are interpreted as follows. The trailer follows the
dotcmd on the same line. The secondline is sent on a separate line
following the dotcmd and trailer. The thirdline is sent after
that. Of the four arguments, dotcmd and thirdline are not subject
to further expansion. All other arguments are further expanded if necessary.

The roffcmd macro illustrates the complexity of dot-commands for the 
divers groff macro packages. E.g., a section title for the man 
package should look as
        
    .SH "Section Title"
        
    while the same command for the ms macro package must be sent as
        
    .SH
    Section Title
    .PP
        
    The roffcmd macro can be used to send these commands to the output 
    file as follows:
        
    COMMENT(For the man output format:)
    roffcmd(.SH)("Section Title")()()

    COMMENT(For the ms output format:)
    roffcmd(.SH)()(Section Title)(.PP)()
        
    o  sgmlcommand(cmd): sends the SGML command cmd when in SGML 
conversion mode. The cmd is not further expanded.
    o  sgmltag(tag)(onoff): sends <tag> when onoff is nonzero,
or sends </tag> when onoff is zero. Only active in SGML conversions.
    o  txtcommand(cmd): implemented for compatibility reasons, though a
`command' in plain ASCII output doesn't make much sense. The usefulness of
this macro is rather in the fact that it only produces output when in ASCII
conversion mode.

The above commands can be used to quickly implement a macro. E.g., the
macro package implements the it macro (which starts an item in a list) as:
        
    DEFINEMACRO(it)(0)(
        latexcommand(\item )
        htmlcommand(<li> )
        ....
    )
        
    Depending on the output format, it()  applies one of the above 
expansions.

The above described formatcommand() macros are implemented to send not 
further expanded strings (i.e., commands) to the output. The macro package 
also implements whenformat() macros to send any text, which is 
then subject to further expansion. These when...() macros are:
    
    o  whenlatex(text): sends text when in LaTeX conversion mode,
    o  whenhtml(text): sends text when in HTML conversion mode,
    o  whenman(text): sends text when in man conversion mode,
    o  whenms(text): sends text when in ms conversion mode,
    o  whentxt(text): sends text when in ASCII conversion mode,
    o  whensgml(text): sends text when in SGML conversion mode.

Once again, note that the difference between the
whenformat() macros and the formatcommand() macros is,
that the former expands their argument while the latter does not. As an
example, consider the following code fragment:
        
    You are now reading
        whenlatex(a LaTeX-generated 
                  footnote(LaTeX is a great 
                   document language!)
                  document)
        whenhtml(a HTML document via your
                 favorite browser)
        
    The whenformat() macros are used here to make sure that the 
arguments to the macros are further expanded; this makes sure that the 
footnote macro in the whenlatex block gets treated as a footnote.


4.3.2: Figures

        Figures in format-independent documents are a problem. You cannot avoid
contact with the final format (HTML, LaTeX or whatever) if you want to include
figures in a text.

Yodl approaches figures as follows:
    
    o  Figures can only be included in LaTeX, HTML and XML documents.
    o  For LaTeX, you must prepare a picture in an external file that is
included in the document as en encapsulated PostScript file.
Incidentally, that means that epsf must be stated as one of the LaTeX
styles using the latexoptions macro.  The default, however, can be
modified using the setlatexfigureext() macro.
    

    The file in question is stated in Yodl without an extension. Yodl provides
a default extension, .ps.
    o  For HTML and XML, you must prepare a picture in an external file that
is placed in the document using the  tag. The file must
have the default extension (.jpg) or the extension specified with the
sethtmlfigureext() macro.
    o  All other output formats do not include pictures in the document, but
    typeset something like insert figure .. here.

The macro to include a figure is called, appropriately, figure. It
takes three arguments:
    
    o  The first argument is the filename. This name may include directories,
but may not include the filename extension. The reason for this is, that
Yodl supplies the correct extension once the output format is known.
    o  The second argument is the figure title, or the caption. Yodl prefixes
this caption with the text Figure xx:, where xx is a number.
    o  The last argument is a label, which Yodl defines as a placeholder for
the figure number.

For example, you might draw a picture or scan a photo and put it in a
.jpg file, for usage with HTML documents. The conversion to PostScript
could be automated, e.g., using a Yodl macro:
        
    SYSTEM(xpmtoppm picture.xpm | pnmtops > picture.ps)
        
    See section 3.1.64 for details about using the SYSTEM macro.

After this, you would be reasonably safe that the picture is available for
both HTML and LaTeX output. The picture would be typeset in a figure using:
        
    figure(picture)
    (A photo of me.)
    (photo)
        
    Note how the first argument, the filename, does not contain an
extension. The third argument, which is a label, can be used in, e.g.,
        
    See figure ref(photo) for a photograph showing me.
        
    Yodl has a several auxiliary macros, which are:
    
    o  fig(label): This macro is a shorthand for getfigurestring()
ref(label). It just makes typing shorter, and is used as e.g.: See
fig(photo) for a photograph. Note that the string figure that is
generated by this macro can be (re)defined, see below.
    o  setfigurestring(name): This macro is similar to
setchapterstring etc.. It defines the string that is used to identify a
figure, and is (appropriately) figure by default. The macro
getfigurestring() expands to the string in question. See also section
4.3.5.1 for a discussion of national language support.
    o  sethtmlfigureext(.new): This macro redefines the filename
extension for HTML conversions from .gif to .new. Note that you must
include a leading dot in the redefinition.
    

    The new extension is used in the first following figure statement.
    o  sethtmlfigurealign(align): This redefines the alignment of
figures in HTML, which is default bottom. Check your HTML handbook for
possible options; top and center should be fairly standard.
    o  setlatexfigureext(.new): Redefines the extension from .ps to
.new.


4.3.3: Fonts and sizes

        Yodl's standard macro package supports the following macros to change fonts:
    
    o  bf(text): sets text in boldface.
    o  em(text): sets text emphasized, usually in italics.
    o  tt(text): sets text in teletype. 

Furthermore, the tt() macro does not expand macros occurring
inside its argument. That means that you can safely write:
        
    In Yodl, you can use tt(includefile(somefile)) to include a file
    in your document.
        
    The tt() macro should not be used for long listings of verbatim text;
use verb() to set code samples etc..

Yodl's standard macro package has no commands to change font sizes, as the
size is changed internally when appropriate (e.g., in section titles), nor is
there a default macro to define other font-families.


4.3.4: Labels, links, references and URLs

        
    References such as see ... for more information are very common in
documents. Yodl supports three mechanisms to accomplish such references:
    
    o Labels and references: Labels can be defined in a document as a
placeholder for the last number used in a sectioning command. At other points
in the document, references to those labels are used. The reference expands to
the number, as in see section 1.3.

This mechanism is available in all output formats. Furthermore, the
numeric reference (1.3 in the example of the previous paragraph) is in HTML a
clickable reference that leads to the mentioned section.
    o Labels and links: This mechanism can be used to set links in a
document without using the number of a sectioning command, as in see the
introduction for more information, with the introduction being a
clickable link to some label. 

This mechanism of course only leads to a clickable link in HTML: in other
formats the text see the etc. is just typeset as is.
    o URLs: Universal Resource Locators (URLs) are used to create links to
other HTML documents or services, like HTML's  method.  The
URLs of course only result in clickable links in HTML output; in other output
formats only some descriptive text appears.

The above mechanism is implemented by the following macros:
    
    o  The macro label(name) defines a label named name. The
name of the label can be used in a ref or link macro.
        o  The macro ref(name) sets a reference to the label named
name.  The text of the reference is the number of the last sectioning
command that was active during the creation of the label. When using
references it is therefore important to define the corresponding labels right
after a sectioning command, as in
        
    section(How to install my program) label(howtoinstall)
    This section describes...
    ...
    See section ref(howtoinstall) for installation instructions.
        
    The macro ref(howtoinstall) expands to the number of the 
section named How to install my program.
    o  The macro link(description)(name) always expands to the
description. In HTML output, a clickable link is created pointing to a
label called name. For example:
        
    label(megahard)
    COMMENT(sigh...)
    The Jodel package isn't shareware, it isn't
    beggarware, it isn't freeware, it's
    bf(megahard-ware).
    ...
    Who wants a link(picosoft)(megahard)?
        
    This code fragment would always set the text picosoft, but under HTML
a clickable link would appear pointing to link(the text)(megahard).
    o  The macro url(description)(location) always expands to the
description, but creates a hyperlink pointing to location in HTML.
For example,
        
    Take a look at my 
    url(homepage)(http://www.somewhere.nl/karel/karel.html).
        
    The text homepage always
appears, but only in HTML it is a link. (Note that the double quotes, which
are necessary in HTML around the location, are not required by Yodl.) To use a
different font in the description part, surrond it inside the url
parameter list, as in:
        
    The Yodl package can be obtained at the site tt(ftp.rug.nl) in the
    directory url(tt(/contrib/frank/software/yodl))
                 (ftp://ftp.rug.nl/contrib/frank/software/yodl).
        
    o  The macro email(address) is a special case of url: under
HTML, the address appears as a clickable link in slanted font to mail
address. For example:
        
    I can be reached at
    email(f.b.brokken@rug.nl).
        
    I can be reached at f.b.brokken@rug.nl <f.b.brokken@rug.nl>.

Always keep in mind that the name of a label must be exactly identical in
both the label macro and in the ref or link macro. Other than
that, the name is irrelevant.

Furthermore, note that lincludefile is yet another macro defining a
label: it includes a file and automatically creates a label just before the
included file's text. That means that a Yodl file like:
        
    chapter(Introduction)
    sect(Welcome)
    lincludefile(WELCOME)(welcome)

    chapter(Technical information)
    lincludefile(TECHINFO)(techinfo)
        
    creates two labels: WELCOME and TECHINFO.

Here are  some final thoughts about using labels and references:
    
    o  Don't put `weird' characters in label names. Generally, don't use
spaces and tabs.
    o  The name of the label is always only an internal symbol; it does
not appear in the output. Therefore, constructions such as the following are
not correct:
        
    ref(em(labelname))
        
    The reason for the incorrectness is, what internal name should
em(labelname) generate? Here probably an attempt is made to set a
reference in italics. The right construction is of course to set whatever
ref() returns in italics, as in:
        
    em(ref(labelname))
        
    o  The label macro should not appear nested inside another
macro.  There is no strict reason for this as far as Yodl is concerned;
however, the processors of Yodl's output might go haywire. E.g., beware of the
construction
        
    section(Introduction label(intro))
        
    The right form being
        
    section(Introduction)label(intro)
        
    (linking to intro usually does not show Introduction), or:
        
    label(intro)section(Introduction) 
        
    (linking to intro usually does show Introduction).


4.3.5: Lists and environments

            Yodl's default macros support the following lists and environments:

By default, the following lists are available:
    
    o Description lists: A description list consists of a list of elements,
where each element starts with a short (usually bold faced) description. The
description list is generated by the description() macro. The
elements of the list start with dit(). The dit() 
macro expects a short description of the item.

Example:
        
    A description list:
    description(
    dit(First this:) One item.
    dit(Then this:) Another item.
    )
        
    o Enumeraton lists: An enumeration list consist of sequentially
numbered elements.  The list is generated by the enumeration()
macro. Its elements start with the eit() macro.

Example:
    
    An enumerated list:    
    enumeration(    
    eit() One item.    
    eit() Another item.    
    )    
        
    o Itemized lists: An itemized lists consists of indented items, usually
    preceded by a bullet. 

An itemized list is produced by the itemization() macro, which has one
argument: the items themselves. These items must start with it().

Example:
        
    An itemized list:
    itemization(
    it() One item.
    it() Another item.
    )
            

Specialized environments are:
    
    o Centered text: Centering text may not be available in all output 
    formats. When unavailable, the text is typeset left-flushed.

Centered text is generated by the center() macro. Line brakes within
centered text may be obtained using the nl() macro.

Example:
        
    center(
    Centered text. nl()    
    Another line of centered text.
    )    
        
    o Verbatim text: Verbatim text appears on the output exactly in the
    same layout as it is in the input file. Typesetting text in verbatim mode
    is useful for, e.g., source files. Depending on the output format, the
    font of the verbatim text is changed to a teletype font.

The text must either be inside the verb() macro. For example:
        
    verb(
        This is totally verbatim text.
        It is not further processed by Yodl.
    )
        
    The verbatim text is of course not subject to macro expansion by Yodl.
Note, however, that SUBST transformations will take place, as these
substitutions take place during the lexical scanning phase of Yodl's input,
and are not part of the macro-expansion process. See also section 3.1.62.

Furthermore, if a character translation table has been defined, the
argument of the verb() macro will also be subject to character
table transformations. By temporarily suppressing the active character table
(see section PUSHCHARTABLE [PUSHCHARTABLE]) this can be prevented.
    o Quotations: Quotations are usually indented with respect to their
surrounding text. It is for the author to decided whether the quoted text
should be typeset normally, or that it should be bold-faced or emphasized. To
insert a quotation use the quote() macro:
        
    Shakespeare once wrote:
    quote(
        ``To be or not to be, that's the question''
    )
        


4.3.5.1: National language support

        Yodl includes rudimentary national language support (NLS), in the sense that
it allows you to redefine the strings identifying chapters or parts, or the
strings identifying figures. E.g., a command chapter(Introduction) 
by default results in the text Chapter 1: Introduction.

Using the setchapterstring(text) macro, the Chapter text can be
redefined.  E.g., in a Dutch text you might put
        
    setchapterstring(Hoofdstuk)
        
    somewhere near the beginning of your document. Similar to
setchapterstring, a macro getchapterstring exists returning the
text identifying chapters.  (Internally, getchapterstring is of course
used to actually set the text).  To redefine the text to identify a part, use
setpartstring(text); to redefine the text to identify a figure, use
setfigurestring(text).

The set....string macros only influence how Yodl names chapters or
parts in HTML, man, ms or txt output. LaTeX output is not
affected, since LaTeX does its own NLS. Usually, NLS is present for LaTeX as a
`style file' named, e.g., dutch.sty. Therefore, if you want a Dutch
document, you need to:
    
    o  put latexpackage(dutch)(babel)in the preamble of
the document. This ensures that LaTeX uses Dutch abbreviation rules.
    o  redefine the chapter and part names for non-LaTeX output, using:
        
    setlanguage(dutch)
        
    o  Finally, you should probably type your text in Dutch.

The setlanguage() macro expects one argument: the name of the language
that is used. See section 4.2 for details about this macro. The
setlanguage() macro redefines the language-dependent section (and other)
headers, and depends on the availability of the corresponding
language<name>() macro, where <name> is the name of the language (by
convention <name> states the english name of the language). 
Currently, languagedutch(), languageenglish() (the default), 
and languageportugese() are available. It's easy to expand this little set
with macros for other languages. The setlanguage() macro merely requires
the specification of the language. For example:
        
    setlanguage(english)
        
    This macro installs the following defaults (corresponding translations
should be defined for other languages):
        
    settocstring(Table of Contents)
    setaffilstring(Affiliation)
    setauthorstring(Author)
    setchapterstring(Chapter)
    setdatestring(Date)
    setfigurestring(Figure)
    setpartstring(Part)
    settitlestring(Title)
        


4.3.5.2: Pagebreaks after the title and table of contents

            Yodl inserts  page-breaks in a limited number of cases:
    
    o  A pagebreak is generated after the title information in book and
report documents.
    o  A pagebreak is generated after a table of contents in all documents.

So, when a document has both title information and a table of contents
then whatever follows next normally starts on a separate page.  Furthermore,
if the document is a book or a report, the title and table of contents
will also be separated by pagebreaks.

This behavior can be modified using the (no)titleclearpage() and
(no)tocclearpage() directives, further described in section
4.3.7.


4.3.6: Sectioning

        This section describes the sectioning commands for articles, reports,
books and for plainhtml. The document type manpage defines its own
sectioning commands (cf. section 4.1.2:
    
    o  part(title): Starts a new part. Only available in book 
documents. 
    o  chapter(title): Starts a new chapter. Only available in book 
or report documents.
    o  sect(title): Starts a section. 
    o  subsect(title): A subsection.
    o  subsubsect(title): A sub-subsection.
    o  subsubsubsect(title): An even smaller sectioning command.

These macros generate entries in the table of contents and use numbering,
which means that each section is prefixed with a number (1, 1.1, 1.2, and so
on).  The macros are also available with an n prefix (npart,
nchapter, nsect etc.) which generate neither entries in the table of
contents nor numbers. The n-versions can be used in, e.g., an article
where the sectioning commands should show their captions, but not any numbers
generated by default.

Sectioning should always start at the top level sections of the available
document: chapter for reports, sect for articles, etc.. If you start a
document with a lower sectioning command (e.g., when you start an article with
a subsect), the numbering of sections may go haywire. The only exception
to this rule is the part of a book document: parts are optional, in
books, chapters may be the top sectioning commands.  Summarizing, books or
reports should start with chapter.  Articles should start with
sections.

The sectioning commands have a further function: when label statements 
appear after the sectioning command, then a label name is used as a 
placeholder for the last generated number. This is further described in 
section 4.3.4.


4.3.7: Typesetting modifiers

        This section lists various macros that can be used to modify the looks of your
document. When used, these macros must appear before stating the document
type with article, report, book, manpage or plainhtml.
    
    o  abstract(text): This macro is relevant for all output formats.
The text is added to the document after the title, author and date
information, but before the table of contents. The abstract is usually set as
a quote, in italics font (though this depends on the output format).
Abstracts are supported in articles and reports, but not in other
document types. I.e., if you need introductory text in a book, you should
start with a non-numbered chapter that holds this text.
    o  affiliation(site): This macro is relevant for article,
report and book documents. It defines the affiliation of the
author. The site information appears in the title, below the author's
name.
    o  htmlbodyopt(option)(value): This macro adds option="value" to
the <body> tag that is generated for HTML output. The HTML converter
generates <body> tags each time that a new file is started; i.e., at the
top of the document and at each chapter-file. Different HTML browsers support
different <body> tag options, but useful ones may be e.g.:
        
    htmlbodyopt(fgcolor)(#000000)
    htmlbodyopt(bgcolor)(#FFFFFF)
        
    This defines the foreground color as pure white (red/green/blue all 0) and
the background color as black (red/green/blue all hexadecimal FF, or 255).
Another useful option may be htmlbodyopt(background) (some.gif), defining
some.gif as the page background.

See the documentation on HTML for more information.

Note that value is automatically surrounded by double quotes when 
this macro is used. They should not be used by authors using this macro.
    o  latexdocumentclass(class): This macro forces the
    \documentclass{...} setting in LaTeX output to class.
    o  latexlayoutcmds(commands): This macro can be used to specify your
own LaTeX layout commands. When present, the commands are placed in LaTeX
output following the \documentclass definition.
    o  latexoptions(options): This macro is only relevant for LaTeX
output formats, it is not expanded in other formats. The options are used
in LaTeX's \documentclass definition; e.g., a useful option might be
dina4. Multiple options should be separate by commas, according to the
LaTeX convention.
    o  latexpackage(options)(name): This macro is only relevant for
LaTeX output formats, it is not expanded in other formats. Each package
should have its own latexpackage() statement. If there are no options, the
options argument should remain empty. Here is an example using this macro:
        
    latexpackage(dutch)(babel)
        
    o  mailto(email): The mailto macro is only expanded in HTML
documents, it is ignored in other formats. It defines where mail about the
document should be sent to.
    o  nosloppyhfuzz(): By default, the LaTeX output contains the text
        
    \hfuzz=4pt
        
    which is placed there by the macro package. This suppresses overfull
hbox warnings of LaTeX when the overfull-ness is less than 4pt.  Use
nosloppyhfuzz() to get the standard LaTeX warnings about overfull hboxes.
    o  notableofcontents(): As the name suggests, this macro suppresses
the generation of the table of contents. For HTML that means that no
clickable index of sections appears after the document title.

The table of contents is by default suppressed in plainhtml and
manpage documents.
    o  notitleclearpage(): Normally, Yodl inserts a clearpage()
directive after typesetting title information in book or report
documents, but not in article documents. Use notitleclearpage to
suppress this directive.
    o  notocclearpage() (no table-of-contents clear-page): In all
document types, Yodl inserts a clearpage() directive following the table
of contents. Use notocclearpage() to suppress that.
    o  noxlatin(): The LaTeX output contains by default the command to
include the file xlatin1.tex, distributed with Yodl. This file maps
Latin-1 characters to LaTeX-understandable codes and makes sure that you can
type characters such as ü, and still make them processable by LaTeX. If
you don't want this, put noxlatin() in the preamble.
    o  standardlayout(): This is another LaTeX option.  Use
standardlayout() to get `vanilla' LaTeX layout, possibly indenting
paragraphs and using fairly limited vertical spacing between paragraphs.
This macro is ignored for other conversion types.
    o  titleclearpage(): Forces the insertion of a clearpage()
directive after the title information has been typeset. This behavior is the
default in book and report documents. See also notitleclearpage().
    o  tocclearpage(): Forces the insertion of a clearpage()
directive following the table of contents. This behavior is default in all
document types; the macro is provided for consistency reasons with
(no)titleclearpage().

Note again: these modifiers must appear before the document type
definition.


4.3.8: Miscellaneous commands

            The following is a list of commands that don't fall in one of the above
categories. 
    
    o  clearpage(): This macro starts a new page in LaTeX. For HTML, a
horizontal rule is shown. (Note that the macro package sometimes inserts new
pages by itself; e.g., following a table of contents. See also section
4.3.7 for a discussion of (no)titleclearpage() and
(no)tocclearpage().)
    o  def(macro)(nrofarguments)(definition): This defines a new macro
macro having nrofarguments arguments, and expanding to
definition. The markers ARGx, where x is 1, 2, etc., can be
used in the definition part to indicate where arguments should be pasted
in. This macro is a shorthand for DEFINEMACRO, see section
3.1.11.
    o  footnote(text): This macro sets text as a footnote when the
output format allows it. When not, the text is set in parentheses.
    o  gagmacrowarning(name name ...): This macro suppresses yodl's
warnings cannot expand possible user macro name, where name is a
candidate macro name. gagmacrowarning is a synonym for NOUSERMACRO,
described in section 3.1.41.
    

    E.g., if your document contains "as for manpages, see sed(1), tr(1) and
awk(1)", and if you get tired of warnings about possible user macros sed, tr
and awk, try the following:
        
    gagmacrowarning(sed tr awk)
    ...
    As for manpages, see sed(1), tr(1) and awk(1).
        
    o  htmlnewfile(): Starts a new subfile in HTML output. This stanza
is also automatically generated when the HTML converter encounters a
chapter directive. Using htmlnewfile, the output can be split at
any point. However make sure that the subfile is still reachable; e.g., by
creating a clickable link with label and ref, or label and
link.
    o  includefile(file): Includes file and defines a label (see the
label macro) with the same name. Furthermore, a message about the
inclusion is shown on the screen. The file is searched for relative to the
directory of the file in which the includefile macro was used (or relative
to the directory where the yodl run was started when the
--legacy-include or -L option was provided) and also in the
system-wide include directory. The default extension .yo is supplied if
necessary.
    

    The lincludefile macro is handy in the following situation:
        
    chapter(Introduction)
    lincludefile(INTRO)(intro)
        
    This fragment starts a chapter and includes a file. Here the label name
(INTRO) can also be used to refer to the chapter as the lincludefile
stanza appears immediately following the corresponding
sectioning command.
    o  nl(): Forces a new line. Some output formats may produce an error
upon the usage of nl() in `unexpected' places; e.g., LaTeX won't allow new
lines in the footnote text (as defined in the footnote macro). Using
nl() in running text should however be ok. Example:
        
    This line is nl()
    broken in two.
        
    o  redefinemacro(macro)(nrofargs)(redef): This command (re)defines a
macro, expecting nrofargs arguments, to redef. If a previous
definition of the macro existed, it is overruled. Example:
        
    redefinemacro(clearpage)(0)(\ 
    em(---New page starts here---))
        
    Use ARGx in the redef part to indicate where all arguments 
should occur, as in the following imaginary macro to typeset a literature
reference:
        
    redefinemacro(litref)(3)(
        Title: bf(ARG1) nl()
        Author(s): em(ARG2) nl()
        Published by: ARG3
    )
    ...
    litref(Java in a Nutshell)
      (David Flanagan)
      (O'Reilly & Associates, Inc.)
        
    The redefinemacro statement also has a shorthand called redef.


4.4: Locations of the macros
    
    The files defining the macros are by default installed to the directory
/usr/local/share/yodl during Yodl's installation process (Note that this
diverts from an earlier default: /usr/local/lib/yodl; furthermore, 
some systems or some distributions may use other locations).

The files in this directory are organized as follows:
    
    o  The files that should be read for a particular conversion are named
after their conversion, e.g., latex.yo and html.yo. These files must
be processed by Yodl before your document can be converted accordingly. The
provided yodl2... scripts take care of that automatically.
    o  All support counters, symbols and macros are defined in files named
std.<conversion>.yo, e.g., std.html.yo, std.latex.yo. These files may
be modified without notice, and are an essential part of the Yodl macros. They
should not be modified by hand, as they are created by the macro generating
process. 
    o  The predefined character tables are found in files names
chartables/<conversion>.yo.

The (binary) Yodl package contains the following programs and support
files:
    
    o  The yodl program itself, which generates converted document(s);
    o  The yodlpost postprocessor, which performs fixups for conversion
formats. Using yodlpost is required for formats whose documents 
cannot be created in one pass by yodl itself;
    o  Auxiliary scripts such as yodl2tex, yodl2html;
    o  The macros and character tables for the various conversion types;
    o  The raw macros and the macro-generating scripts;
    o  The documentation (html and manual pages)

The source Yodl package contains all the sources files, installation
guides, change-logs etc., that are required to compile the binary
programs. Those who want to compile Yodl themselves, must have a C
compiler (preferably the Gnu C compiler) available, and preferably the
icmake program maintenance utility. Basic support for make is provided
as well.


Chapter 5: Conversions and converters

Each macro package handling a conversion from Yodl to a given output format
has its peculiarities. Although the various macro packages are very similar,
they do show some differences, due to the unique characteristics of the output
formats. Normally, these differences should not cause difficulties in
performing the conversion(s). In this chapter the conversion of a Yodl
document is covered. The currently supported document types are discussed. 
Furthermore, in this chapter the new post processor yodlpost is
described as well as a little support program: yodlverbinsert.


5.1: Conversion script invocations

    Yodl is distributed with scripts  named yodl2latex, yodl2html and 
other yodl2... drivers. Invocations like
        
    yodl2latex file
        
    causes Yodl to process file.yo and to write output to
file.latex. The extension of the input file, .yo, is the default Yodl
extension; the extension of the output file, .latex, is given by the name
of the shell script. Analogously, yodl2html writes to a file having the
extension .html.

The conversion scripts auto-load the macro file appropriate for the
conversion: latex.yo for LaTeX conversions, html.yo for HTML
conversions, etc.. The macro files are in Yodl's standard include directory
(which is mentioned in Yodl's usage information when Yodl is started without
arguments). If the include directory is altered in such a way that it doesn't
contain a path to the default directory anymore, then Yodl won't be able to
auto-load the conversion specific macro files, producing unexpected
results. This can be prevented by specifying the literal text $STD_INCLUDE
in a user-defined path setting.

When the conversion scripts themselves are started without arguments, usage
information is shown about the conversion scripts.

Depending on the conversion type, the following output is produced:
    
    o  For LaTeX conversions, one output file with the extension .latex
is written. 
    o  For HTML conversions, several files may be written; one file per
chapter of the original document. When the document is not sectioned by
chapters, only one output file is produced.

The `main' output file always has the name of the input file but with
extension .html. This file holds the document title and the table of
contents. When more than one output files are created, then they are named
name01.html, name02.html etc., where name is the original name of
the input file. E.g., a document prog.yo might lead to prog.html,
prog01.html etc..
    
    o  For man conversions, one output file with the extension .man is
written. 
    o  For text conversions, the converter is named yodl2txt and one 
output file with the extension .txt is created.
    o  For XML conversions, the converter is named yodl2xml and output
files are produced comparably to the way they are produced with the html
conversion: one file per chapter if chapters are used, otherwise one single
output file, having the extension(s) .xml.

The `second-phase' scripts, distributed with earlier versions of Yodl, are
no longer part of Yodl's distribution, as they do not relate directly to
Yodl's actions. They may remain useful, though, as leftovers from earlier
distributions.
    


5.2: The HTML converter
    
    HTML doesn't support automatic section numbering or resolving of
label/reference pairs. The converter takes care of this. Other target
languages (e.g., XML, text) suffer from the same problems.


5.2.0.1: Direct commands to HTML

        Similar to the LaTeX converter, you can use either NOTRANS or
htmlcommand to send HTML commands to the output. Or, since the only 
`difficult' characters are probably only < and >, you can also resort 
to CHAR for these two characters.

Furthermore, the HTML converter defines the macro htmltag, expecting two 
arguments: the tag to set, and an `on/off' switch. E.g., htmltag(b)(1) 
sets  while htmltag(b)(0) sets .

E.g., the following code sends a HTML command 
 to the output file when 
in HTML mode:
        COMMENT(-- alternative 1, using htmlcommand --)
    htmlcommand(
)
    
    COMMENT(-- alternative 2, using NOTRANS --)
    IFDEF(html)(
        NOTRANS(<hr>)
    )()
    
    COMMENT(-- alternative 3, using CHAR --)
    IFDEF(html)(
        CHAR(<)hrCHAR(>)
    )()
        
    COMMENT(-- alternative 4, using htmltag --)
    htmltag(hr)(1)
        


5.2.0.2: Section numbering

        The HTML converter numbers its own sections. This is handled internally.
However, the current converter only can number sections as starting at 1, and
outputs the numbers in arabic numerals (you can't number with A, B, etc..).


5.3: The LaTeX converter
    
    The LaTeX converter is, from Yodl's viewpoint, an easy one: since
LaTeX supports wide functionality, a Yodl document is basically just
re-mapped to LaTeX commands. No post-processing by yodlpost is
required.


5.3.0.1: Direct commands to LaTeX
    
        To send LaTeX commands directly to the output, use the latexcommand()
macro (see section 4.3.1), or use NOTRANS (see section
3.1.40). The advantage of the latexcommand macro is that it only
outputs its argument when in LaTeX mode.

The following two code fragments both output \pagestyle{plain} when in 
LaTeX mode: 
        
    COMMENT(-- First alternative: --)
    latexcommand(\pagestyle{plain})
    
    COMMENT(-- Second alternative: --)
    IFDEF(latex)(
        NOTRANS(\pagestyle{plain})
    )()
         


5.3.0.2: Verbatim text
    
        The Yodl macro package defines two macros that generate verbatim text (e.g.,
source code listings). These macros are verb() and tt().
    
    o verb The verb() macro and is meant for longer listings (whole
files); as in:
        
        verb(
    #include <stdio.h>
    
    int main (int argc, char **argv)
    {
        printf ("Hello World!\n");
        return 0;
    }
        )
        
    The verb() macro generates \begin{verbatim} and
\end{verbatim} when used in LaTeX conversion mode.
That means that (in that situation) the verb macro has only one caveat:
you cannot put \end{verbatim} into it.
    o tt The tt() macro also inserts verbatim text. It is used for
short in-line strings (e.g, **argv). The LaTeX converter doesn't
actually use a verbatim mode, but sets the characters in teletype font.


5.4: The man converter
    
    Manual pages can be constructed using the special yodl2man converter.
This converter assumes that the manual page has been designed using the
manpage() macro. Yodl (and thus the yodl2man converter, when converting
man-pages, skips all leading white space on lines. Paragraphs are supported,
though. An empty line separates paragraphs.


5.4.0.1: Direct commands to man

        Either NOTRANS or mancommand can be used to send man commands to the
output. 

E.g., the following code sends a MAN command 
 to the output file when 
in MAN mode:
        COMMENT(-- alternative 1, using mancommand --)
    mancommand(
)
    
    COMMENT(-- alternative 2, using NOTRANS --)
    IFDEF(man)(
        NOTRANS(<hr>)
    )()
        


5.5: The txt converter
    
    Plain text documents can be constructed using the yodl2txt converter.
This converter resolves all references into the document itself, so
postprocessing is required. 


5.5.0.1: Direct commands to txt

        Either NOTRANS or txtcommand can be used to send txt commands to the
output. 

E.g., the following code sends a TXT command 
 to the output file when 
in TXT mode:
        COMMENT(-- alternative 1, using txtcommand --)
    txtcommand(
)
    
    COMMENT(-- alternative 2, using NOTRANS --)
    IFDEF(txt)(
        NOTRANS(<hr>)
    )()
        


5.6: The experimental XML converter
    
    The XML converter is experimental. It was added to Yodl to allow me to write
documents for the horrible `webplatform' of the university of Groningen. The
XML support files (located in the xml directory in the standard macro's
directory) clearly reflect this target. Although experimental, they were kept
because the XML macros support interesting constructions allowing Yodl to
handle closing tags somewhat more strict than required for HTML.


5.7: The Yodl Post-processor `yodlpost'

    Following the conversion of a Yodl text, most target-languages require an
additional operation, called `post-processing'. Post-processing is required
for various reasons: to split the output in separate files (HTML, XML); to
fixup the locations of labels, that are referred to earlier than the labels
are defined (virtually all target language except LaTeX); tables of contents
are available only after the conversion, but have to be inserted at the
beginning of the document; etc. etc..

Starting with Yodl V. 2.00 there is only one post-processor, handling all
the conversions for all target languages. Program maintenance of just one
program is certainly easier than maintenance of as many programs as there are
target-languages, at the expense of only a slightly larger program: after all,
the one post-processor contains the conversion procedures for all target
languages. It turns out that this is a very minimal drawback. See section
6.7 for the technical details of post-processor program
maintenance. 

The post-processor that is distributed since Yodl V. 2.00 does not use the
.tt(Yodl)TAGSTART. and .tt(Yodl)TAGEND. tags anymore. Instead, the conversion
process produces a index file in which comparable information is
written. The advantage of using an index file is that the postprocessor
doesn't have to parse the output file generated by Yodl twice (once to
determine the tags, once to process the tags), which by itself accelerates the
conversion process; and (albeit of a somewhat limited practical importance)
that the tags are no longer reserved words: authors may put
.tt(Yodl)TAGSTART. and .tt(Yodl)TAGEND. into their texts as often as they
want. 

Authors should be aware of some caveats with respect to some target languages:
    
    o man- and ms- conversions all dots are converted by the active
character conversion table to \&.. Commands in these languages always
start with a dot as the first character on a line. In order to insert these
commands the roffcmd() (see section MACROLIST) should be used.
    o plain text conversions As stated before, the ASCII converter
basically only strips macronames from its input. This converter is so basic,
that it should only be used as a last
resort, when no other target language is available for the job.
        

    With the plain text converer, the layout of the input file is very
important, as the output is basically the same as the input. The only
exception to this rule are multiple empty lines, which normally are consumed
by the post-processor, to be replaced by one single empty line.
    o sgml conversions the SGML converter was implemented for historic
reasons. It is by no means complete, and can at best be considered an `initial
starting point'. Currently, the SGML converter only supports the article
document type, having sect as its top-level sectioning command.
    o xml conversions The XML converter was implemented to allow me
(Frank) to produce XML text as defined by the so-called `webplatform' of the
University of Groningen. A completely pathological implementation of XML,
crippling its users to the level of the `double click brigade'. Well, so be
it. The net result of this is that Yodl now offers some basic form  of XML
conversion. After adding XML conversion, however, there was never any real
situation where it could profitably be used. Therefore, further development of
the XML conversion has, for the time being, been suspended.


5.8: The support program `yodlverbinsert'

        The program yodlverbinsert is a simple C support program that
can be used to generate verb()-sections in Yodl files
from sections of existing files. The files from which sections are included
are usually C or Cpp source files, accepting either // or
/*-style comment. 

Yodlverbinsert offers the possibility to indent both the initial
verb-statement and the inserted file contents. Furthermore, an additional
empty line may be inserted before the first line that is actually inserted.
The program is invoked according to the following synopsis:


yodlverbinsert [OPTIONS] marker file


The arguments have the following meanings;
    
    o  marker

    The argument marker must start in file's first column en must
either start as a standard C or C++ comment: // or /* must be
used. Following that, the remainder of the argument is used as a label, e.g.,
//label, /*LABEL*/. The label may contain non-alpha characters as
well. Except for the first two characters and their locations no special
restrictions imposed upon the label texts. A labeled section ends at the next
//= (when the label started with //) or at the next /**/ (when the
label started with /*). Like the labels, the end-markers must also start
in the file's first column.
    o  file

    The argument file must be an existing file. Yodlverbinsert was
designed with C or C++ sources in minde, from which labeled sections
must be inserted into a Yodl document, but file could also refer to
another type of (text) file.

The default values of options are listed below, with each of the options
between square brackets. The defaults were chosen so that yodlverbinsert
performs the behavior of an earlier version of this program, which was
not distributed with Yodl.
    
    o  -N

    Do not write a newline immediately following verb-statement's
open-parenthesis. By default it is written, causing an additional line to be
inserted before the first line that's actually inserted from a file.
    o  -s spaces [0]

        start each line that is written into the verb-section with
spaces additional blanks.
    o  -S spaces [8]

        prefix the verb of the verb-section by 
spaces additional blanks.
    o  -t tabs [0]

        start each line that is written into the verb-section with
tabs additional tab characters. If both -s and -t are specified,
the tabs are inserted first.
    o  -T tabs [0]

        prefix the verb of the verb-section by tabs additional tab
characters. If both -S and -T are specified, the tabs are inserted
first.

Yodlverbinsert writes its selected section to its standard output
stream.


5.8.1: Example


Assume the file demo contains the following text:
        
preceding text

//one
one 1

//=

/*two*/

    two

/**/

trailing text
    

Then the following commands write the shown output to the program's
standard output:
    
    o  verbinclude //one demo

                verb(
one 1

)

    o  verbinclude -N //one demo

                verb(one 1

)

    o  verbinclude -s4 '/*two*/' demo

                verb(
    
        two
    
)


To call yodlverbinsert from a Yodl document, use
PIPETHROUGH. E.g., 
        
    PIPETHROUGH(yodlverbinsert //one demo)
        

Alternatively, define a simple macro like the macro verbinsert:
    
    
DEFINEMACRO(verbinsert)(2)(PIPETHROUGH(yodlverbinsert //ARG1 ARG2)()\ 
)
    
    which may be a useful macro if all or most of your labeled sections start
with //, and if yodlverbinsert's arguments don't vary much. Variants
to this macro can easily be conceived of.


Chapter 6: Technical information

This chapter consists of various sections. The first section describes Yodl
from the point of view of the systems administrator. Issues such as the
installation of the package are addressed here. The second section describes
Yodl's technical implementation in some detail. Apart from the documentation
about Yodl given here, much can be found in the individual source
files. However, section 6.2 describes `the broad
picture'. Having read section 6.2, it should be relatively easy
to determine what happens where inside the Yodl program and the yodl-post
post processor.


6.1: Obtaining Yodl

    Yodl and the distributed macro package can be obtained from
https://fbb-git.gitlab.io/yodl/. The associated git-repository page is 
located at https://gitlab.com/fbb-git/yodl.

Yodl can also be retrieved as a binary Debian package: to find it at 
http://www.debian.org/distrib/packages by entering yodl (in any
distribution) in the form-fields you'll find on that page.


6.1.1: Installing Yodl

            The binary package, distributed in yodl-X.Y.Z_a.b.c.deb can be
installed using dpkg -install yodl-X.Y.Z. It installs:
    
    o  Yodl's binaries in /usr/bin;
    o  Yodl's macros in /usr/share/yodl
    o  Yodl's documentation in /usr/share/doc/yodl;
    o  Yodl's manpages in /usr/share/man/man{1,7};

Local installations, not using the Debian installation process, can be
obtained using the provided icmake build-script see below. An alternative
(cf. contrib/build.pl) is to use the contributed build.pl script. Note
that build.pl is not maintained by me. If you bump against problems when
using it, I'll probably not be able to help you out.

If a local installation is preferred or required, 
unpack the file yodl-X.Y.Z.tar.gz. Next, chdir to the directory 
yodl-X.Y.Z, and optionally tweak the file
config to your needs. Next, issue the command:
        
    build programs    (or use `build programs strip' to strip the binaries)
    build macros
    build man
    build manual
        
    followed by 
        
   install programs WHERE        (install the programs under WHERE,
                                  e.g. install programs /usr/bin)

   install macros WHERE          (install the macros under WHERE
                                  e.g., install macros /usr/share/yodl)

   install man WHERE             (install the man-pages under WHERE
                                  e.g., install man /usr/share/man)
                                
   install manual WHERE          (install the manual under WHERE
                                  e.g., install manual /usr/share/doc/yodl)

   install docs WHERE            (install additional docs under WHERE
                                  e.g., install docs /usr/share/doc/yodl)
        

The installation process installs the binaries, manual pages, other
documentation and macro files under the indicated directories. 

However, by far the easiest way to install a binary distribution is to use
the Debian dpkg --install yodl*.deb command. Dpkg installs the
various parts according to Debian's conventions under usr/. 

Installation from source requires you to have the following programs
installed on your system: 
    
    o  A recent C compiler and run-time environment. A POSIX-compliant
compiler, libraries and set of header files should work without problems. 
    o  A recent installation of Icmake: Icmake is part of the
standard Debian distribution, and can also be obtained from 
https://fbb-git.gitlab.io/icmake/
    o  Standard tools, like sed, grep, perl, etc..
    o  /bin/sh: a POSIX-compliant shell interpreter. The GNU shell
interpreter bash can be used instead.


6.2: Organization of the software

    This section describes the organization of the source files. Its contents are
not necessarily relevant for the binary distribution. The section is probably
most useful to those readers who want to be able to extend or who want to do
maintenance on Yodl's sources, or who want simply to understand what's
happening inside the Yodl program. 

Much of the documentation is provided in the individual source files
themselves. This section, however, should offer the `broad picture', allowing
you to understand the logic behind Yodl relatively fast.


6.2.1: Subdirectories and their meanings

        After unpacking Yodl's source archive, the following directories are available:
    
    o  yodl: the root-directory of the Yodl tree. All sources and
program maintenance scripts are found in or below this directory.
    o  yodl/macros: This directory contains all the macro
definitions of the standard macro package. It contains the following
subdirectories: 
        
        o  yodl/macros/in: This directory contains 
generic macro files. These macro files contain the word @STD_INCLUDE@,
which is replaced by the standard include directory used in a particular
distribution.
        o  yodl/macros/rawmacros: This directory contains the raw
macro definition files themselves. One file per raw macro. A raw macro
contains the implementations of that macro for all supported conversion
types, and has the extension .raw. Furthermore, this directory contains
some support scripts: create, separator.pl, startdoc.pl.
        o  yodl/macros/yodl: this is the directory to contain Yodl's
standard macros. The (recursive) contents of this directory is eventually
copied by the installation procedure to the .../share/yodl directory,
which then becomes Yodl's standard include directory.
        o  yodl/macros/yodl/chartables: This directory contains 
character-translation tables for various target languages.
        o  yodl/macros/yodl/xml: This directory contains the XML frame
files, used to convert Yodl documents to XML, as implemented by the
`webplatform' of the University of Groningen. All these frame files have the
extensions .xml.

o  yodl/man: The raw source files of all man-pages:
manpages of the Yodl program itself, of the yodl post-processor, of the
conversion scripts, of the builtin-functions, of the standard macros and of
Yodl's manpage and letter document types. These raw source files have
the extensions .in, indicating that they may contain @STD_INCLUDE@
words, which is replaced by the eventually used standard include path.
        
        o  yodl/man/1: The destination for Yodl's manual pages in
section 1 (programs).
        o  yodl/man/7: The destination for Yodl's manual pages in
section 7 (macro packages and conventions).

o  yodl/manual: The source files of the complete
Yodl manual, as well as the directories for the various converted formats.
    The script build, found in this directory, constructs the manual in
the subdirectories:
        
        o  yodl/manual/html: the HTML-converted manual;
        o  yodl/manual/latex: the LaTeX-version of the manual;
        o  yodl/manual/pdf: the pdf-version of the manual;
        o  yodl/manual/ps: the PostScript-version of the manual;
        o  yodl/manual/txt: the plain text-version of the manual;

o  yodl/manual/: The source files of the complete
    The Yodl document files themselves are located in subdirectories of this
directory. They are:
        
        o  yodl/manual/converters
        o  yodl/manual/intro
        o  yodl/manual/macros
        o  yodl/manual/technical
        o  yodl/manual/userguide (and various subdirectories)

o  yodl/scripts: support scripts used by the building process:
configreplacements replaces @XXX@ words by their actual values as
found in yodl/src/config.h; yodl2whatever.in is the generic
yodl-converter, calling macros specific for a particular conversion type. This
generic converter is installed in .../bin/, together with specific
converters, installed as soft-links to this generic converter.
    o  Yodl's base directory contains sub-directories holding the source
files of the C programs Yodl and yodl-post, as well as all auxiliary
directories containing sources of the (logical) components of these
programs. Most of these components are like C++ classes in that they
define a building block of the Yodl and/or yodl-post program. Their
organization, interaction and relationship is described below. They are:
        
        o  yodl/args: the component handling the command-line
arguments; 
        o  yodl/builtin: the component handling Yodl's builtin
functions;
        o  yodl/chartab: the component handling Yodl's
character table type;
        o  yodl/counter: the component handling Yodl's
counter type;
        o  yodl/file:  the component handling all file
operations (locating, opening, etc.);
        o  yodl/hashitem: key/value combinations stored in
Yodl's hashtable;
        o  yodl/hashmap: Yodl's hashtable;
        o  yodl/lexer: Yodl's lexical scanner: this component
consumes the .yo file, and produces a continuous stream of tokens to be
handled by another component: the parser.
        o  yodl/lines: the component storing lines of text,
used by yodl-post. 
        o  yodl/macro: the component handling Yodl's
macro type;
        o  yodl/message: the component handling all messages
(warnings, errors, verbosity settings, etc.).
        o  yodl/new: the component handling all memory
allocations (except for duplicating strings, which is handled by the
root-component). 
        o  yodl/ostream: the component handling all Yodl's
output to its output-file (Yodl may also output to strings, which is not
handled by the ostream component). 
        o  yodl/parser: the component handling the tokens
produced by the lexer-component. This component governs all actions to be
taken during a conversion. Its actions all derive from its function
parser_process(). 
        o  yodl/postqueue: the component handling the
postprocessing required by most conversions.
        o  yodl/process: the component handling the execution
of child- or system-processes.
        o  yodl/queue: the component allowing the lexical
scanner to queue its input, awaiting further processing. 
        o  yodl/root: the component defining some basic
typedefs and enumerations, as well as the new_str() function duplicating a
string, and the out_of_memory() function handling memory allocation
failures. 
        o  yodl/stack: the component implementing a stack
data structure.
        o  yodl/string:  the component implementing a
text-storage data structure and its functionality.
        o  yodl/strvector:  the component implementing a table of
SUBST key-value pairs.
        o  yodl/subst:  the component handling Yodl's
SUBST definitions;
        o  yodl/symbol:  the component handling Yodl's
symbol type;
        o  yodl/yodl: the sources of the Yodl program
itself. This directory also contains the implementations of all builtin
functions, whose filenames all start with gram_ (E.g.,
gramaddtocounter.c). 
        o  yodl/yodlpost: the sources of the yodl-post
program. 

The script build, found in this directory, compiles  the programs
and macros, storing them in:
        
        o  tmp/install/usr/bin (the binary programs)
        o  tmp/install/usr/share/yodl (the macros)
        o  tmp/install/usr/share/man (the man-pages)
        o  tmp/install/usr/share/doc (the manual and additional
                documentation) 


6.3: Yodl's component interrelations and component setup

        Yodl's components show a strict hierarchical ordering. This allows the testing
and development of components placed nearer to the component's tree without
considering anything that's placed farther away.

The following piece of `ascii-art' shows the relationships for the Yodl
program. The root of the tree starts at the top, at the root component. 
The tree can be read from the top to the bottom, where each horizontal line
starts a level of components mentioned immediately below it, and each vertical
route through the figure a series of components whose functioning depend on at
least the components mentioned earlier. 

However, a more natural way to look at it is to start somewhere in the
tree, and see what's envountered going up. Doing so, all components that
are required are visited. Once the figure shows a 
        
        |
    --- | ---
        |
        
    construction. This means that the horizontal line is not related to the
vertical dependency crossing (but not touching) it.


                                root
                                |                        
                                message
                                |
                                new
                                |                             
                    +-------+---+-------+
                    |       |           |                    
                    string  queue       stack                
                    |       |           |                    
    +--+--+---------+       |           hashitem               
    |  |  |         |       |           |                    
    |  |  strvector |       |           |                    
    |  |  |         |       |           |                    
    |  |  +---------+       |           |                    
    |  |            |       |           |                    
    |  args         subst   |           hashmap              
    |  |            |       |           |                    
    |  |            +-------+       +---+-------+
    |  |                    |       |           |
    |  |                    |       symbol  +---+----+-------+-------+
    |  |                    |       |       |        |       |       |
    |  +------------+------ | ------+       chartab  counter macro   builtin
    |               |       |               |        |       |       |     
    |               file    |               +---+----+-------+-------+
    |               |       |                   |
    |               +---+---+                   |                         
    |                   |                       |
    |               +---+---+                   |
    |               |       |                   |
    process         lexer   ostream             |
    |               |       |                   |
    |               +-------+-------+-----------+
    |                               |
    |                               parser 
    |                               |
    +-------------------------------+
                                    |
                                    (yodl)   
    

A similar, albeit much simpler, tree can be drawn for yodl-post. Here
is the organization of the components for the yodl-post program:
        
                                root
                                |                        
                                message
                                |
                                new
                                |                             
                      +-----+---+---+
                      |     |       |
                      |     |       |
                      lines string  hashitem
                      |     |       |
                      |     args    hashmap
                      |     |       |
                      |     +-------+
                      |     |
                      |     file
                      |     |
                      +-----+
                            |
                            postqueue
                            |
                            yodl2html-post
        

The source files of each component are organized as follows:
    
    o  All the files of a component are stored in a directory, named after
the component. For example, the counter component is found in the
directory
        
    yodl/counter
        
    containing all the (source) files that define that component.
    o  Each function is stored in a file of its own inside its 
component-directory. For example, the function counter_value() is defined
in the source file countervalue.c.
    o  The file names are identical to the names of the functions, except for
the fact that only lower case letters are used for the file names, and that
the file names never use underscore characters. 
    o  The .h header files declare the functions that can be used by
other components. These functions are comparable to C++'s public
members. Furthermore, these .h files define all structs and typedefs that
are required for other components to use a particular component. For example,
the component.h header file may contain
        
#ifndef _INCLUDED_COUNTER_H_
#define _INCLUDED_COUNTER_H_

#include "../root/root.h"
#include "../hashmap/hashmap.h"

void        counter_add(HashItem *item, int add);   /* err  if no counter   */
bool        counter_has_value(int *valuePtr, HashItem *item);
Result      counter_insert(HashMap *symtab, char const *key, int value);
void        counter_set(HashItem *item, int value); /* err  if no counter   */
char const *counter_text(HashItem *item);       /* returns static buffer    */
int         counter_value(HashItem *item);      /* err  if no stack/item    */

#endif
        
    o  All functions declared in .h file start with the name of the
component, and often contain an initial pointer to some struct containing
the essential fields that are associated with that particular component. For
example, most counter_ functions have a HashItem * as their first
argument, as a HashItem is normally used to store the details about a
counter. 
    o  The modifier const is used with pointers to indicate that the
information pointed to by the pointer is `owned' by the provider of that
information. With parameters it indicates that the caller owns the
information, and the function will not modify the provided info; with return
types it indicates that the function `owns' the returned information, which
therefore may not be modified (or freed) by the caller of that function (e.g.,
char const *counter_text). The absence of const in combination with
pointers indicates that the information pointed to by the pointer could, in
principle, be modified by the code receiving the pointer value.
    o  Most components also show a .ih file, a so-called internal
header file. The internal header declares `internal support functions', not
to be used by other parts of the software, and defines internal
typedefs. Since they are an essential ingredient of the component, all these
internal headers start to include the component's .h file, followed by the
declarations of the `private' functions. All these private functions start
with abbreviated component names, like co_ in the case of counters. Here
is a possible implementation of the counter.ih internal header file:
        
#include "counter.h"

#include <stdio.h>

#include "../stack/stack.h"
#include "../message/message.h"
#include "../new/new.h"

Stack  *co_construct(int value);
Stack  *co_sp(HashItem *item, bool errOnFailure);
        
    o  The combination of .h and .ih files define the dependencies
of the component in the component hierarchy. As can be seen, counter
depends on stack, message, new, hashmap and root. The actual
dependency listing may be a bit more complex, as some .h files themselves
depend on other .h files. This is clearly visible in the counter.h
file. The class hierarchy given earlier shows the final component
dependencies.
    o  A .h file of a component X never includes a .ih
file of component Y, but only the .h files of other components. 


6.4: The token-producer `lexer_lex()'

        Tokens are produced by the lexical scanner. The function lexer_lex()
produces the next token, which is always an element of the following set:
        
    TOKEN_UNKNOWN,          /* should never be returned */

    TOKEN_SYMBOL,     
    TOKEN_TEXT,         
    TOKEN_PLAINCHAR,        /* formerly: anychar */
    TOKEN_OPENPAR,
    TOKEN_CLOSEPAR,
    TOKEN_PLUS,             /* it's semantics what we do with a +, not      */
                            /* something for the lexer to worry about       */

    TOKEN_SPACE,            /* Blanks should be at the end                  */
    TOKEN_NEWLINE,

    TOKEN_EOR,              /* end of record: ends pushed strings           */
    TOKEN_EOF,              /* at the end of nested evaluations/eof         */
        

In particular note the existence of a TOKEN_EOR token: this token
indicates the end of a piece of text, a string, inserted into the input stream
by the parser's actions, when it calls lexer_push_str(). Such a
situation occurs in particular when a macro is evaluated: having read a macro,
and replacing its parameters ARG1, ARG2, ... ARGn by their respective
argumentes, the resulting string is pushed back into the input stream by
lexer_push_str(). This happens, e.g., inside the function
p_expand_macro(). An excerpt from this function shows this call:
        
    void p_expand_macro(register Parser *pp, register HashItem *item)
    {
        ...
            if (argc)                           /* macro with arguments     */
                p_macro_args(pp, &expansion, argc);
            ...
            lexer_push_str(&pp->d_lexer, string_str(&expansion));
        ...
    }
        

The parser repeatedly calls the lexer's function lexer_lex(). This happens
most dramatically inside the function p_parse(), defined by a mere single
statement:
        
    void p_parse(register Parser *pp)
    {
        while ((*pp->d_handler[lexer_lex(&pp->d_lexer)])(pp))
            ;
    }
        
    Here, in a loop continuing until the handler indicates that the loop
should terminate, lexer_lex() is called to produce the next token. The
finite state automaton (FSA) implemented here is described in more detail in
section 6.5.

Apart from here, lexer_lex() is called from four other locations
inside the parser component:
    
    o  parser_parlist() repeatedly calls lexer_lex() to obtain all
the tokens associated with a parameter list;
    o  p_handle_default_newline() repeatedly calls lexer_lex() to
obtain all the tokens until all consecutive spaces and newlines are read. This
is one of the handlers of the parser FSA [PARSERFSA];
    o  p_no_user_macro() calls lexer_lex() to determine whether a
`no user macro' has been detected;
    o  p_plus_series() calls lexer_lex() to determine whether a
+symbol has been encountered.

So, lexer_lex() is the parser's `window to the outside world'. The
lexer_lex() function, however, is a fairly complex animal:
    
    o  lexer_lex(): returns next token.  It calls l_lex() to
retrieve the next character from the info waiting to be read;
    o  l_lex(): calls l_nextchar() to obtain the next token, and
appends all char-tokens to the lexer's matched text buffer. Potential compound
symbols (words, numbers) are combined by l_compound() and are then
returned as TOKEN_PLAINCHAR or as a compound token like TOKEN_IDENT;
    o  l_nextchar(): calls l_get() to get the next character, and
handles escape chars, including \ at eoln;
    o  l_get(): if there are no media left, EOF is returned.  If
there are media left, then l_subst_get() retrieves the next character,
handling possible SUBST definitions. At the end of the current input
buffer (memory buffer or file) l_pop() attempts to reactivate the previous
buffer. If this succeeds, EOR is returned, otherwise EOF is returned.
So, the lexer is not able to switch between truly nested media, as in
EVAL() calls, but is able to switch between nested buffers resulting from
replacing macro calls by their definitions;
    o  l_subst_get(): calls l_media_get() to get the next char from
the media. The next char is passed to subst_find() which is a FSA trying to
match the longest SUBST. This may be done repeatedly, and eventually
subst_text() either returns a substitution text, or the next plain
character. A substitution text is pushed onto the lexer's media buffer. The
next character returned is then the next one to appear at the lexer's media
buffer;
    o  l_media_get(): If the current active source of information is a
file, it returns the next character from that file or EOF if no such char
is available anymore.  If the current active source is a memory buffer then
the next char from the buffer is returned. If the buffer is empty EOF is
returned. The media buffer is a circular, self-expanding Queue.


6.5: The Parser's Finite State Automaton

        The  input files are parsed by  the function
parser_process(), which is called by Yodl's main() function.

This processor pushes all files that were specified on the input in reverse
order on the input stack, and then calls the support function p_parse() to
process each of them in turn.

p_parse() is an very short function: it contains one while statement,
repeatedly calling a handler appropriate  with the next token returned
by the lexical scanner. Therefore, the parser can be considered as a table
driven finite state automaton (FSA). 

The table itself is initialized in parser/psetuphandlerset.c, by the
function p_setup_handlerSet(). It fills the two dimensional array
ps_handlerSet with the address of the function that must be called for
each combination of parser-state (as defined in the HANDLER_SET_ELEMENTS
enum) in parser/parser.h and token that may be produced by the lexical
scanner (as defined in the LEXER_TOKEN enum in lexer/lexer.h).
Depending on the situation the parser encounters, it may point its pointer
d_handler to a particular row in this table. Since the rows represent
the parser's states, states can be switched easily by reassigning this
pointer. This happens all the time. For example, when in
parsernameparlist.c a name must be retrieved from a parameter list, it
calls  parser_parlist(pp, COLLECT_SET), which function temporarily
switches the parser's state to COLLECT_SET, returning the parameter list's
contents. to its caller.

The functions whose addresses are stored in the various column-elements of the
array ps_handlerSet are called handler. Most handlers are named
p_handle_<state>_<lextoken>(), where <state> is the name of the
associated parser state, and <lextoken> is the name of the appropriate
lexical scanner token. For example, p_handle_default_symbol() is the
handler that was designed for the situation where the parser is in its
initial, or default, state, and the lexical scanner returns a TOKEN_SYMBOL
token. Some handlers have more generic names, like p_handle_unknown(),
which is some sort of emergengy exit, called when the parser doesn't know what
to do with the received lexical scanner token (a situation which should, of
course, not happen).

In version 2.00, the following handler functions are available:
    
    o  p_handle_insert(Parser *pp): insert matched text
    o  p_handle_default_eof(Parser *pp): return false
    o  p_handle_default_newline(Parser *pp): series of \n's
    o  p_handle_default_plus(Parser *pp): handle + series
    o  p_handle_default_symbol(Parser *pp): handle all symbols
    o  p_handle_ignore(Parser *pp): ignores token
    o  p_handle_ignore_closepar(Parser *pp): handle openpar
    o  p_handle_ignore_openpar(Parser *pp): handle openpar
    o  p_handle_noexpand_plus(Parser *pp): handle + series
    o  p_handle_noexpand_symbol(Parser *pp): handle executed symbols in
        NOEXPAND
    o  p_handle_parlist_closepar(Parser *pp): handle closepar
    o  p_handle_parlist_openpar(Parser *pp): handle openpar
    o  p_handle_skipws_unget(Parser *pp): unget received text 
    o  p_handle_unexpected_eof(Parser *pp): EMERG exit
    o  p_handle_unknown(Parser *pp): emergency exit

The parser has the following states: 
    
    o COLLECT_SET 

       retrieves parameter lists as they are encountered on the input. The
        parameter list is not processed in any way, and omits the surrounding
        parentheses. So, when entering this state (e.g., in the function
        parser_parlist()), a parameter list is completely consumed, but
        only its contents (and not its surrounding parentheses) become
        available. In fact, when entering a state, p_parse() can be called
        again to process the information in this state. Eventually a state
        will encounter some stopping signal (e.g., a non-nested close
        parenthesis in the collect-state results in
        p_handle_parlist_closepar() to return false, thus terminating
        p_parse()), terminating that particular state. The function
        parser_parlist() shows this process in further detail.
    o DEFAULT_SET 

       In this state macros, builtins etc. are processed.  For most of the
        tokens that can be returned by the lexical scanner
        p_handle_insert() is called.   o  When receiving EOF
        it tries to switch to the next file on the stack (or stop), o  When
        receiving a symbol, it either handles them as plain symbols or as
        macros, o  When receiving newlines they are handled (maybe merging
        them by calling a paragraph handler (if defined)), o  Series of +
        characters are handled o  All other tokens are inserted into the
        current output medium (which may be a file, but it may also be a
        memory buffer).  
    o IGNORE_SET 
 
       In this state a parameter list is completely skipped. This state is
        used, for example, when processing COMMENT().
    o NOEXPAND_SET 

       The contents of a parameter list is not expanded, but CHAR builtins
        are processed. In Yodl version 2.00 there is only one situation
        where this state (and its companion state NOTRANS_SET) is actively
        used: Yodl's function gram_NOEXPAND() uses these states to
        retrieve the contents of a no-expanded or no-transed parameter list.
    o NOTRANS_SET 

       When the parser is in this state, a parameter list is inserted using
        the currently active insertion function (inserting to file or memory)
        It is identical to the NOEXPAND_SET state, but the character
        translation table is not used in the NOTRANS_STATE, whereas it is used
        in the NOEXPAND_STATE.
    o SKIPWS_SET

       In this state all white-space characters are consumed. The lexical
        scanner merely returns the next non-whitespace character. This state
        is used, e.g., to skip the white space between multiple parameter
        lists when they are defined for macros.


6.6: Adding a new macro

    With the advent of Yodl V 2.00, raw macros files are introduced. A raw
macro file defines one macro, and all of its conversions. The raw macro
files must be organized as follows:
        
    <STARTDOC>
    macro(name(arg1)(arg2)(etc))
    ( 

        Description of the macro `name', having arguments `arg1', `arg2',
        `etc', each argument is given its own parameter list. The names of the
        arguments in this description should be chosen in such a way that they
        suggest their function or purpose. All macro descriptions starting
        with tt(<STARTDOC>) are included in both the `man yodlmacros'
        manpage and the description of the macro in the user guide. If this is
        not considered appropriate (e.g., tt(XX...()) macros are not described
        in these documents) then use tt(<COMMENT>) rather than
        tt(<STARTDOC>). 
    )
    <>
    DEFINEMACRO(name)(#)(
        statements of macro `name' expecting `#' arguments used by all
        conversions. This section is optional
    <html>
        statements that should be executed by the HTML converter
    <man ms>
        statements that should be executed by two converters. In this case,
        the `man' and `ms' converters
    <else>
        statements that should be executed by all converters not explicitly
        mentioned above
    <>
        statements of macro `name' expecting `#' arguments used by all
        conversions, having processed their specific statements. 
        This section is also optional
    )
        
    When setting up these macro definitions, the <> tags must appear with
the initial documentation section. It must also appear when at least one
specific converter tag is used. For a macro which is converter independent,
the macro definition doesn't contain these pointed-arrow tags. 

When writing standard Yodl macros, each macro should be stored in a file
`name'.raw, where `name' is the lower-case name of the macro. This
file should then be kept in the macros/rawmacros directory. The
macros/build std call then adds the macro (filtering only the required
statements per conversion) to each of the standard conversion formats.

If the macro requires a counter or symbol, consider defining the counter
or symbol in, respectively, @counters and @symbols. Furthermore,
consider pushing and popping these `variables', rather than plain
assigning them, to allow other macros to use the variables as well. A case in
point is the counter XXone which was added to the set of counters
representing a local counter. Macros may always push XXone and pop
Xxone, but should never reassign XXone before its value has been
pushed. For Yodl version 2.00 only XXone was required, but other local
counters might be considered useful in the future. In that case, XXtwo,
XXthree etc. are used. For local symbold XXs prefixes are used:
XXsone, XXstwo, etc.


6.7: The Yodl post-processor

    With Yodl version 2.00 the old-style post-processor has ceased to exist. Also,
the .tt(Yodl)TAGSTART. and .tt(Yodl)TAGEND. symbols no longer appear in
yodl's output. 

Instead, a system using an index file was adopted. When converting
information, yodl produces an output file and an associated index
file. The index file defines offsets in the output file up to where
certain actions are to be performed. Each line in the index file contains the
required information of one directive for yodlpost. For example:
        
    0 set extension man
    53 ignorews
    2112 verb on
    2166 verb off
    80007 ignorews
    80065 copy
    80065 mandone
        
    Entries can be written into the index file using the INTERNALINDEX
builtin function. This function has one argument: the information following
the offset where it is called. So, there will be a INTERNALINDEX(set
extension man) in the macro definitions for this particular conversion
(obviously it is a man conversion. The particular INTERNALINDEX call
is found in the standard man.yo macro definition file). 

When yodlmacros is called, it processes the directives on the idx
file in two steps:
    
    o  First, it reads all directives, and constructs a queue of actions to
perform. During this phase it solves all references to, e.g., labels
defined in the s processed by yodl. This queue is constructed by a
PostQueue object, during its construction phase. 

Postprocessing is realized by a template-method design pattern-like
construction in C.

The algorithm proceeds as follows:

Each element of the index file is read, and its keyword (the word
following the offset) is determined. Then the 'construct' function associated
with that keyword is called. The `construct' functions return pointers to
HashItem elements, which areprocessed by storing them either into the the
symbol table or into the work-queue. The construct functions can use all
PostQueue, New, Message String Args and File functions. Which function
is actually called is determined in the file yodlpost/data.c, where the
array Task task[] is initialized. Task structs have three elements:
        
        o  char const *d_key points to the name of the keyword that 
triggers the corresponding Task struct;
        o  HashItem *(*d_constructor)(char const *key, char *rest)
points to the function that is called when the task struct is created.
        o   void (*d_handler)(long offset, HashItem *item) points to the
function that is called when the queue is processed.

o  Then, when all commands are available, the queued commands are
processed. For this, the appropriate 'handle' functions are called. 

For example, when the INTERNALINDEX(htmllabel ...) is specified, the
function construct_label() is called. This function receives a line line
        
    432 label Overview
        
    meaning that this label has been defined in offset 432 in the file
generated by yodl. The construct_label() function now:
    
    o  Stores the current section number, the filecount and the
sectionnumber in a HashItem.
    o  Stores the hashitem inside its hash-table.

Then, when the queue is processed, a reference to this label may be
encountered. This is signalled by an INTERNALINDEX(ref Overview) call. In
this case the construct_ref() function doesn't have to do much. Here it is
the handler that's doing all the work: 
    
    o  First it looks up the label in the symbol table. The label should be
there, as a result of the earlier construction of the symbol table during the
postqueue_construct() call. 
    o  Then it copies the file written by yodl up to the offset
mentioned in the the ref command.
    o  Then (since we're talking about an html-specific reference) the
appropriate <a href=... command is inserted into the current output file.

When references are solved in text-files, the INTERNALINDEX(txtref
...) command is used. Here, construct_ref() can still be used, but a
specific handle_txt_ref() function is required. 

New postprocessing labels can be constructed easily:
    
    o  Add an element to the array Task task[] in
src/yodlpost/data.c. For example, add a line like:
        
    {"verb",            construct_verb,         handle_verb},
        
    o  Declare the functions in yodlpost.h:
        
    HashItem *construct_verb(char const *key, char *rest);
    void handle_verb(long offset, HashItem *item);
        
    o  The construct_verb() function receives the key (e.g., verb)
and any information that may be available beyond the key as a trimmed line
(not beginning or ending in white space). The construct function should return
a pointer to a hashitem, which can be constructed by
hashitem_construct(). This function should be called with the following
arguments:
        
        o  VOIDPTR;
        o  a pointer to some text to be stored as the hashitem's key (use an
empty string if nothing needs to be stored in a hashtable);
        o  A pointer to the information associated with the key (use 0 if no
information is used; use (void *)intValue to store an int value. Note
that this is not (void *)&intValue: it is the value of the variable
that is interpreted as a pointer here).
        o  The function that handles the destruction of the
value-information. Use free if some information was actually allocated and
must be freed. E.g.,
        
    hashitem_construct(VOIDPTR, "", new_str(rest), free);
        
    Use root_nop if no allocation took place. E.g.,
        
    hashitem_construct(VOIDPTR, "", (void *)s_lastLabelNr, root_nop);
        
    Often the constructor doesn't have to do anything at all. In that case,
initialize the Task element with the existing construct_nop
function. E.g., 
        
    {"drainws",         construct_nop,          handle_drain_ws},
        
    o  The handle_verb() function is called when the file produced by
yodl is processed by postqueue_process(). This happens immediately
after postqueue_construct(). The handler is called with two arguments: 
        
        o  Its first argument is the offset where the INTERNALINDEX call
was generated. The handler should make sure that yodl's output file is
processed up to this offset. Not any further. If a simple copy is required the
function file_copy2offset() is available. E.g.,
        
    file_copy2offset(global.d_out, postqueue_istream(), offset);
        
    Note its arguments: the output and input file pointers are available
through, respectively, global.d_out and postqueue_istream(). 
        o  Its second argument is a pointer to the hashitem struct
originally created by the matching construct...() function. The handler
should not free the information it receives. The function
postqueue_process() takes care of that. 

Examples of actual construct...() and handle...() functions can be
found in src/yodlpost. 

