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Lexing(3)			 OCaml library			     Lexing(3)

NAME
       Lexing -	The run-time library for lexers	generated by ocamllex.

Module
       Module	Lexing

Documentation
       Module Lexing
	: sig end

       The run-time library for	lexers generated by ocamllex .

       === Positions ===

       type position = {
	pos_fname : string ;
	pos_lnum : int ;
	pos_bol	: int ;
	pos_cnum : int ;
	}

       A value of type position	describes a point in a source file.  pos_fname
       is the file name; pos_lnum is the line number; pos_bol is the offset of
       the  beginning  of the line (number of characters between the beginning
       of the lexbuf and the beginning of the line); pos_cnum is the offset of
       the  position (number of	characters between the beginning of the	lexbuf
       and the position).  The difference between pos_cnum and pos_bol is  the
       character offset	within the line	(i.e. the column number, assuming each
       character is one	column wide).

       See the documentation of	type lexbuf for	information about how the lex-
       ing engine will manage positions.

       val dummy_pos : position

       A  value	 of  type position , guaranteed	to be different	from any valid
       position.

       === Lexer buffers ===

       type lexbuf = {
	refill_buff : lexbuf ->	unit ;

       mutable lex_buffer : bytes ;

       mutable lex_buffer_len :	int ;

       mutable lex_abs_pos : int ;

       mutable lex_start_pos : int ;

       mutable lex_curr_pos : int ;

       mutable lex_last_pos : int ;

       mutable lex_last_action : int ;

       mutable lex_eof_reached : bool ;

       mutable lex_mem : int array ;

       mutable lex_start_p : position ;

       mutable lex_curr_p : position ;
	}

       The type	of lexer buffers. A lexer buffer is the	argument passed	to the
       scanning	functions defined by the generated scanners.  The lexer	buffer
       holds the current state of the scanner, plus a function to  refill  the
       buffer from the input.

       At  each	token, the lexing engine will copy lex_curr_p to lex_start_p ,
       then change the pos_cnum	field of lex_curr_p by updating	 it  with  the
       number  of  characters  read since the start of the lexbuf .  The other
       fields are left unchanged by the	lexing engine.	In order to keep  them
       accurate,  they must be initialised before the first use	of the lexbuf,
       and updated by the relevant lexer actions (i.e. at each end of line  --
       see also	new_line ).

       val from_channel	: Pervasives.in_channel	-> lexbuf

       Create  a lexer buffer on the given input channel.  Lexing.from_channel
       inchan returns a	lexer buffer which reads from the input	channel	inchan
       , at the	current	reading	position.

       val from_string : string	-> lexbuf

       Create a	lexer buffer which reads from the given	string.	Reading	starts
       from the	first character	in the string. An  end-of-input	 condition  is
       generated when the end of the string is reached.

       val from_function : (bytes -> int -> int) -> lexbuf

       Create  a  lexer	 buffer	with the given function	as its reading method.
       When the	scanner	needs more characters, it will call  the  given	 func-
       tion,  giving  it  a  byte sequence s and a byte	count n	. The function
       should put n bytes or fewer in s	, starting at index 0, and return  the
       number of bytes provided. A return value	of 0 means end of input.

       === Functions for lexer semantic	actions	===

       === Functions for lexer semantic	actions	===

       ===  The	following functions can	be called from the semantic actions of
       lexer definitions (the ML code enclosed in  braces  that	 computes  the
       value  returned by lexing functions). They give access to the character
       string matched by the regular expression	associated with	 the  semantic
       action.	These functions	must be	applied	to the argument	lexbuf,	which,
       in the code generated by	ocamllex, is bound to the lexer	buffer	passed
       to the parsing function.	===

       val lexeme : lexbuf -> string

       Lexing.lexeme  lexbuf returns the string	matched	by the regular expres-
       sion.

       val lexeme_char : lexbuf	-> int -> char

       Lexing.lexeme_char lexbuf i returns character number i in  the  matched
       string.

       val lexeme_start	: lexbuf -> int

       Lexing.lexeme_start  lexbuf  returns  the offset	in the input stream of
       the first character of the matched string.  The first character of  the
       stream has offset 0.

       val lexeme_end :	lexbuf -> int

       Lexing.lexeme_end  lexbuf returns the offset in the input stream	of the
       character following the last character of the matched string. The first
       character of the	stream has offset 0.

       val lexeme_start_p : lexbuf -> position

       Like  lexeme_start  , but return	a complete position instead of an off-
       set.

       val lexeme_end_p	: lexbuf -> position

       Like lexeme_end , but return a complete position	instead	of an offset.

       val new_line : lexbuf ->	unit

       Update the lex_curr_p field of the lexbuf to reflect the	start of a new
       line.   You  can	 call this function in the semantic action of the rule
       that matches the	end-of-line character.

       Since 3.11.0

       === Miscellaneous functions ===

       val flush_input : lexbuf	-> unit

       Discard the contents of the buffer and reset the	current	position to 0.
       The next	use of the lexbuf will trigger a refill.

       === ===

OCamldoc			  2017-04-30			     Lexing(3)

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