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Lexing(3o) OCaml library Lexing(3o)
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 file and the beginning of the line); pos_cnum is
the offset of the position (number of characters between the beginning of the file and the
position).
See the documentation of type lexbuf for information about how the lexing engine will man-
age 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 : string ;
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 scan-
ner, plus a function to refill the buffer from the input.
Note that the lexing engine will only 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 copied without change 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).
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 : (string -> 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 function, giving it a character string s and
a character count n . The function should put n characters or less in s , starting at
character number 0, and return the number of characters 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 expression.
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 offset.
val lexeme_end_p : lexbuf -> position
Like lexeme_end , but return a complete position instead of an offset.
=== 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 2008-05-19 Lexing(3o)
Generated by $Id: phpMan.php,v 4.49 2006/02/26 13:18:18 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2012-05-24 15:17 @38.107.179.238 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)