# Module Sedlexing

    module Sedlexing: sig .. end

Runtime support for lexers generated by `sedlex`.

This module is roughly equivalent to the module Lexing from the OCaml standard library, except that its lexbuffers handle Unicode code points (OCaml type: `Uchar.t` in the range `0..0x10ffff`) instead of bytes (OCaml type: `char`).

It is possible to have sedlex-generated lexers work on a custom implementation for lex buffers. To do this, define a module `L` which implements the `start`, `next`, `mark` and `backtrack` functions (See the Internal Interface section below for a specification). They need not work on a type named `lexbuf`: you can use the type name you want. Then, just do in your sedlex-processed source, bind this module to the name `Sedlexing` (for instance, with a local module definition: `let module Sedlexing = L in ...`.

Of course, you'll probably want to define functions like `lexeme` to be used in the lexers semantic actions.

    type lexbuf

The type of lexer buffers. A lexer buffer is the argument passed to the scanning functions defined by the generated lexers. The lexer buffer holds the internal information for the scanners, including the code points of the token currently scanned, its position from the beginning of the input stream, and the current position of the lexer.

    exception InvalidCodepoint of int

Raised by some functions to signal that some code point is not compatible with a specified encoding.

    exception MalFormed

Raised by functions in the `Utf8` and `Utf16` modules to report strings which do not comply to the encoding.

Creating generic lexbufs

    val create : ?bytes_per_char:(Stdlib.Uchar.t -> int) ->
           (Stdlib.Uchar.t array -> int -> int -> int) -> lexbuf

Create a generic lexer buffer. When the lexer needs more characters, it will call the given function, giving it an array of Uchars `a`, a position `pos` and a code point count `n`. The function should put `n` code points or less in `a`, starting at position `pos`, and return the number of characters provided. A return value of 0 means end of input. `bytes_per_char` argument is optional. If unspecified, byte positions are the same as code point position.

    val set_position : ?bytes_position:Stdlib.Lexing.position ->
           lexbuf -> Stdlib.Lexing.position -> unit

set the initial tracked input position, in code point, for `lexbuf`. If unspecified, byte postion is set to the same value as code point position.

    val set_filename : lexbuf -> string -> unit

`set_filename lexbuf file` sets the filename to `file` in `lexbuf`. It also sets the `Lexing.pos_fname` field in returned `Lexing.position` records.

    val from_gen : ?bytes_per_char:(Stdlib.Uchar.t -> int) ->
           Stdlib.Uchar.t Gen.t -> lexbuf

Create a lexbuf from a stream of Unicode code points. `bytes_per_char` is optional. If unspecified, byte positions are the same as code point positions.

    val from_int_array : ?bytes_per_char:(Stdlib.Uchar.t -> int) -> int array -> lexbuf

Create a lexbuf from an array of Unicode code points. `bytes_per_char` is optional. If unspecified, byte positions are the same as code point positions.

    val from_uchar_array : ?bytes_per_char:(Stdlib.Uchar.t -> int) ->
           Stdlib.Uchar.t array -> lexbuf

Create a lexbuf from an array of Unicode code points. `bytes_per_char` is optional. If unspecified, byte positions are the same as code point positions.

Interface for lexers semantic actions

The following functions can be called from the semantic actions of lexer definitions. They give access to the character string matched by the regular expression associated with the semantic action.

    val lexeme_start : lexbuf -> int

`Sedlexing.lexeme_start lexbuf` returns the offset in the input stream of the first code point of the matched string. The first code point of the stream has offset 0.

    val lexeme_bytes_start : lexbuf -> int

`Sedlexing.lexeme_start lexbuf` returns the offset in the input stream of the first byte of the matched string. The first code point of the stream has offset 0.

    val lexeme_end : lexbuf -> int

`Sedlexing.lexeme_end lexbuf` returns the offset in the input stream of the character following the last code point of the matched string. The first character of the stream has offset 0.

    val lexeme_bytes_end : lexbuf -> int

`Sedlexing.lexeme_end lexbuf` returns the offset in the input stream of the byte following the last code point of the matched string. The first character of the stream has offset 0.

    val loc : lexbuf -> int * int

`Sedlexing.loc lexbuf` returns the pair `(Sedlexing.lexeme_start lexbuf,Sedlexing.lexeme_end lexbuf)`.

    val bytes_loc : lexbuf -> int * int

`Sedlexing.bytes_loc lexbuf` returns the pair `(Sedlexing.lexeme_bytes_start lexbuf,Sedlexing.lexeme_bytes_end lexbuf)`.

    val lexeme_length : lexbuf -> int

`Sedlexing.lexeme_length lexbuf` returns the difference `(Sedlexing.lexeme_end lexbuf) - (Sedlexing.lexeme_start lexbuf)`, that is, the length (in code points) of the matched string.

    val lexeme_bytes_length : lexbuf -> int

`Sedlexing.lexeme_length lexbuf` returns the difference `(Sedlexing.lexeme_bytes_end lexbuf) - (Sedlexing.lexeme_bytes_start lexbuf)`, that is, the length (in bytes) of the matched string.

    val lexing_positions : lexbuf -> Stdlib.Lexing.position * Stdlib.Lexing.position

`Sedlexing.lexing_positions lexbuf` returns the start and end positions, in code points, of the current token, using a record of type `Lexing.position`. This is intended for consumption by parsers like those generated by `Menhir`.

    val lexing_position_start : lexbuf -> Stdlib.Lexing.position

`Sedlexing.lexing_position_start lexbuf` returns the start position, in code points, of the current token.

    val lexing_position_curr : lexbuf -> Stdlib.Lexing.position

`Sedlexing.lexing_position_curr lexbuf` returns the end position, in code points, of the current token.

    val lexing_bytes_positions : lexbuf -> Stdlib.Lexing.position * Stdlib.Lexing.position

`Sedlexing.lexing_bytes_positions lexbuf` returns the start and end positions, in bytes, of the current token, using a record of type `Lexing.position`. This is intended for consumption by parsers like those generated by `Menhir`.

    val lexing_bytes_position_start : lexbuf -> Stdlib.Lexing.position

`Sedlexing.lexing_bytes_position_start lexbuf` returns the start position, in bytes, of the current token.

    val lexing_bytes_position_curr : lexbuf -> Stdlib.Lexing.position

`Sedlexing.lexing_bytes_position_curr lexbuf` returns the end position, in bytes, of the current token.

    val new_line : lexbuf -> unit

`Sedlexing.new_line lexbuf` increments the line count and sets the beginning of line to the current position, as though a newline character had been encountered in the input.

    val lexeme : lexbuf -> Stdlib.Uchar.t array

`Sedlexing.lexeme lexbuf` returns the string matched by the regular expression as an array of Unicode code point.

    val lexeme_char : lexbuf -> int -> Stdlib.Uchar.t

`Sedlexing.lexeme_char lexbuf pos` returns code point number `pos` in the matched string.

    val sub_lexeme : lexbuf -> int -> int -> Stdlib.Uchar.t array

`Sedlexing.sub_lexeme lexbuf pos len` returns a substring of the string matched by the regular expression as an array of Unicode code point.

    val rollback : lexbuf -> unit

`Sedlexing.rollback lexbuf` puts `lexbuf` back in its configuration before the last lexeme was matched. It is then possible to use another lexer to parse the same characters again. The other functions above in this section should not be used in the semantic action after a call to `Sedlexing.rollback`.

Internal interface

These functions are used internally by the lexers. They could be used to write lexers by hand, or with a lexer generator different from `sedlex`. The lexer buffers have a unique internal slot that can store an integer. They also store a "backtrack" position.

    val start : lexbuf -> unit

`start t` informs the lexer buffer that any code points until the current position can be discarded. The current position become the "start" position as returned by `Sedlexing.lexeme_start`. Moreover, the internal slot is set to `-1` and the backtrack position is set to the current position.

    val next : lexbuf -> Stdlib.Uchar.t option

`next lexbuf` extracts the next code point from the lexer buffer and increments to current position. If the input stream is exhausted, the function returns `None`. If a `'\n'` is encountered, the tracked line number is incremented.

    val __private__next_int : lexbuf -> int

`__private__next_int lexbuf` extracts the next code point from the lexer buffer and increments to current position. If the input stream is exhausted, the function returns -1. If a `'\n'` is encountered, the tracked line number is incremented.

This is a private API, it should not be used by code using this module's API and can be removed at any time.

    val mark : lexbuf -> int -> unit

`mark lexbuf i` stores the integer `i` in the internal slot. The backtrack position is set to the current position.

    val backtrack : lexbuf -> int

`backtrack lexbuf` returns the value stored in the internal slot of the buffer, and performs backtracking (the current position is set to the value of the backtrack position).

    val with_tokenizer : (lexbuf -> 'token) ->
           lexbuf ->
           unit -> 'token * Stdlib.Lexing.position * Stdlib.Lexing.position

`with_tokenizer tokenizer lexbuf` given a lexer and a lexbuf, returns a generator of tokens annotated with positions. This generator can be used with the Menir parser generator's incremental API.

Support for common encodings

    module Latin1: sig .. end

    module Utf8: sig .. end

    module Utf16: sig .. end