# grammar::fa::dacceptor(3tcl) 0.1.1 grammar_fa "Finite automaton operations and usage"

## Name

grammar::fa::dacceptor - Create and use deterministic acceptors

## Synopsis

- package require Tcl 8.4
- package require snit
- package require struct::set
- package require grammar::fa::dacceptor ?0.1.1?

- ::grammar::fa::dacceptor daName fa ?-any any?
- daName option ?arg arg ...?
- daName destroy
- daName accept? symbols

## Description

This package provides a class for acceptors constructed from deterministic finite automatons (DFA). Acceptors are objects which can be given a string of symbols and tell if the DFA they are constructed from would accept that string. For the actual creation of the DFAs the acceptors are based on we have the packages grammar::fa and grammar::fa::op.

## API

The package exports the API described here.

::grammar::fa::dacceptor daName fa ?-any any?

  Creates a new deterministic acceptor with an associated global Tcl command whose name is daName. This command may be used to invoke various operations on the acceptor. It has the following general form:

  daName option ?arg arg ...?

    Option and the args determine the exact behavior of the command. See section ACCEPTOR METHODS for more explanations.

    The acceptor will be based on the deterministic finite automaton stored in the object fa. It will keep a copy of the relevant data of the FA in its own storage, in a form easy to use for its purposes. This also means that changes made to the fa after the construction of the acceptor will not influence the acceptor.

    If any has been specified, then the acceptor will convert all symbols in the input which are unknown to the base FA to that symbol before proceeding with the processing.

## ACCEPTOR METHODS

All acceptors provide the following methods for their manipulation:

daName destroy

  Destroys the automaton, including its storage space and associated command.

daName accept? symbols

  Takes the list of symbols and checks if the FA the acceptor is based on would accept it. The result is a boolean value. True is returned if the symbols are accepted, and False otherwise. Note that bogus symbols in the input are either translated to the any symbol (if specified), or cause the acceptance test to simply fail. No errors will be thrown. The method will process only just that prefix of the input which is enough to fully determine (non-)acceptance.

## EXAMPLES

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category grammar_fa of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

acceptance, acceptor, automaton, finite automaton, grammar, parsing, regular expression, regular grammar, regular languages, state, transducer

## Category

Grammars and finite automata

## Copyright

Copyright © 2004 Andreas Kupries <andreas_kupries@users.sourceforge.net>