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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 ===





       ===  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                          2014-10-18                         Lexing(3)

ocaml 4.02.1 - Generated Sun Oct 19 18:51:37 CDT 2014
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