1Lexing(3)                          OCamldoc                          Lexing(3)
2
3
4

NAME

6       Lexing - The run-time library for lexers generated by ocamllex.
7

Module

9       Module   Lexing
10

Documentation

12       Module Lexing
13        : sig end
14
15
16       The run-time library for lexers generated by ocamllex .
17
18
19
20
21
22
23
24       === Positions ===
25
26
27       type position = {
28        pos_fname : string ;
29        pos_lnum : int ;
30        pos_bol : int ;
31        pos_cnum : int ;
32        }
33
34
35       A value of type position describes a point in a source file.  pos_fname
36       is the file name; pos_lnum is the line number; pos_bol is the offset of
37       the  beginning  of the line (number of characters between the beginning
38       of the lexbuf and the beginning of the line); pos_cnum is the offset of
39       the  position (number of characters between the beginning of the lexbuf
40       and the position).  The difference between pos_cnum and pos_bol is  the
41       character offset within the line (i.e. the column number, assuming each
42       character is one column wide).
43
44       See the documentation of type lexbuf for information about how the lex‐
45       ing engine will manage positions.
46
47
48
49       val dummy_pos : position
50
51       A  value  of  type position , guaranteed to be different from any valid
52       position.
53
54
55
56
57       === Lexer buffers ===
58
59
60       type lexbuf = {
61        refill_buff : lexbuf -> unit ;
62
63       mutable lex_buffer : bytes ;
64
65       mutable lex_buffer_len : int ;
66
67       mutable lex_abs_pos : int ;
68
69       mutable lex_start_pos : int ;
70
71       mutable lex_curr_pos : int ;
72
73       mutable lex_last_pos : int ;
74
75       mutable lex_last_action : int ;
76
77       mutable lex_eof_reached : bool ;
78
79       mutable lex_mem : int array ;
80
81       mutable lex_start_p : position ;
82
83       mutable lex_curr_p : position ;
84        }
85
86
87       The type of lexer buffers. A lexer buffer is the argument passed to the
88       scanning functions defined by the generated scanners.  The lexer buffer
89       holds the current state of the scanner, plus a function to  refill  the
90       buffer from the input.
91
92       At  each token, the lexing engine will copy lex_curr_p to lex_start_p ,
93       then change the pos_cnum field of lex_curr_p by updating  it  with  the
94       number  of  characters  read since the start of the lexbuf .  The other
95       fields are left unchanged by the lexing engine.  In order to keep  them
96       accurate,  they must be initialised before the first use of the lexbuf,
97       and updated by the relevant lexer actions (i.e. at each end of line  --
98       see also new_line ).
99
100
101
102       val from_channel : Pervasives.in_channel -> lexbuf
103
104       Create  a lexer buffer on the given input channel.  Lexing.from_channel
105       inchan returns a lexer buffer which reads from the input channel inchan
106       , at the current reading position.
107
108
109
110       val from_string : string -> lexbuf
111
112       Create a lexer buffer which reads from the given string. Reading starts
113       from the first character in the string. An  end-of-input  condition  is
114       generated when the end of the string is reached.
115
116
117
118       val from_function : (bytes -> int -> int) -> lexbuf
119
120       Create  a  lexer  buffer with the given function as its reading method.
121       When the scanner needs more characters, it will call  the  given  func‐
122       tion,  giving  it  a  byte sequence s and a byte count n . The function
123       should put n bytes or fewer in s , starting at index 0, and return  the
124       number of bytes provided. A return value of 0 means end of input.
125
126
127
128
129       === Functions for lexer semantic actions ===
130
131
132       ===  The following functions can be called from the semantic actions of
133       lexer definitions (the ML code enclosed in  braces  that  computes  the
134       value  returned by lexing functions). They give access to the character
135       string matched by the regular expression associated with  the  semantic
136       action.  These functions must be applied to the argument lexbuf, which,
137       in the code generated by ocamllex, is bound to the lexer buffer  passed
138       to the parsing function. ===
139
140
141       val lexeme : lexbuf -> string
142
143
144       Lexing.lexeme  lexbuf returns the string matched by the regular expres‐
145       sion.
146
147
148
149       val lexeme_char : lexbuf -> int -> char
150
151
152       Lexing.lexeme_char lexbuf i returns character number i in  the  matched
153       string.
154
155
156
157       val lexeme_start : lexbuf -> int
158
159
160       Lexing.lexeme_start  lexbuf  returns  the offset in the input stream of
161       the first character of the matched string.  The first character of  the
162       stream has offset 0.
163
164
165
166       val lexeme_end : lexbuf -> int
167
168
169       Lexing.lexeme_end  lexbuf returns the offset in the input stream of the
170       character following the last character of the matched string. The first
171       character of the stream has offset 0.
172
173
174
175       val lexeme_start_p : lexbuf -> position
176
177       Like  lexeme_start  , but return a complete position instead of an off‐
178       set.
179
180
181
182       val lexeme_end_p : lexbuf -> position
183
184       Like lexeme_end , but return a complete position instead of an offset.
185
186
187
188       val new_line : lexbuf -> unit
189
190       Update the lex_curr_p field of the lexbuf to reflect the start of a new
191       line.   You  can  call this function in the semantic action of the rule
192       that matches the end-of-line character.
193
194
195       Since 3.11.0
196
197
198
199
200       === Miscellaneous functions ===
201
202
203       val flush_input : lexbuf -> unit
204
205       Discard the contents of the buffer and reset the current position to 0.
206       The next use of the lexbuf will trigger a refill.
207
208
209
210
211
2122018-04-14                          source:                          Lexing(3)
Impressum