module Lexing: sig .. end
The run-time library for lexers generated by ocamllex.
Positions
type position = {
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pos_fname : string; |
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pos_lnum : int; |
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pos_bol : int; |
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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 lexing 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 = {
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refill_buff : lexbuf -> unit; |
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mutable lex_buffer : string; |
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mutable lex_buffer_len : int; |
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mutable lex_abs_pos : int; |
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mutable lex_start_pos : int; |
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mutable lex_curr_pos : int; |
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mutable lex_last_pos : int; |
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mutable lex_last_action : int; |
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mutable lex_eof_reached : bool; |
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mutable lex_mem : int array; |
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mutable lex_start_p : position; |
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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 : (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.
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.