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<link title="Sys" rel="Chapter" href="Sys.html"> <link title="Thread" rel="Chapter" href="Thread.html"> <link title="ThreadUnix" rel="Chapter" href="ThreadUnix.html"> <link title="Unix" rel="Chapter" href="Unix.html"> <link title="UnixLabels" rel="Chapter" href="UnixLabels.html"> <link title="Weak" rel="Chapter" href="Weak.html"><link title="Positions" rel="Section" href="#6_Positions"> <link title="Lexer buffers" rel="Section" href="#6_Lexerbuffers"> <link title="Functions for lexer semantic actions" rel="Section" href="#6_Functionsforlexersemanticactions"> <link title="Miscellaneous functions" rel="Section" href="#6_Miscellaneousfunctions"> <title>Lexing</title> </head> <body> <div class="navbar"><a class="pre" href="Lazy.html" title="Lazy">Previous</a> <a class="up" href="index.html" title="Index">Up</a> <a class="post" href="List.html" title="List">Next</a> </div> <h1>Module <a href="type_Lexing.html">Lexing</a></h1> <pre><span class="keyword">module</span> Lexing: <code class="code"><span class="keyword">sig</span></code> <a href="Lexing.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top"> The run-time library for lexers generated by <code class="code">ocamllex</code>.<br> </div> <hr width="100%"> <br> <h6 id="6_Positions">Positions</h6><br> <pre><code><span id="TYPEposition"><span class="keyword">type</span> <code class="type"></code>position</span> = {</code></pre><table class="typetable"> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span id="TYPEELTposition.pos_fname">pos_fname</span> : <code class="type">string</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span id="TYPEELTposition.pos_lnum">pos_lnum</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span id="TYPEELTposition.pos_bol">pos_bol</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span id="TYPEELTposition.pos_cnum">pos_cnum</span> : <code class="type">int</code>;</code></td> </tr></table> } <div class="info "> A value of type <code class="code">position</code> describes a point in a source file. <code class="code">pos_fname</code> is the file name; <code class="code">pos_lnum</code> is the line number; <code class="code">pos_bol</code> is the offset of the beginning of the line (number of characters between the beginning of the lexbuf and the beginning of the line); <code class="code">pos_cnum</code> is the offset of the position (number of characters between the beginning of the lexbuf and the position). The difference between <code class="code">pos_cnum</code> and <code class="code">pos_bol</code> is the character offset within the line (i.e. the column number, assuming each character is one column wide). <p> See the documentation of type <code class="code">lexbuf</code> for information about how the lexing engine will manage positions.<br> </div> <pre><span id="VALdummy_pos"><span class="keyword">val</span> dummy_pos</span> : <code class="type"><a href="Lexing.html#TYPEposition">position</a></code></pre><div class="info "> A value of type <code class="code">position</code>, guaranteed to be different from any valid position.<br> </div> <br> <h6 id="6_Lexerbuffers">Lexer buffers</h6><br> <pre><code><span id="TYPElexbuf"><span class="keyword">type</span> <code class="type"></code>lexbuf</span> = {</code></pre><table class="typetable"> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span id="TYPEELTlexbuf.refill_buff">refill_buff</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> unit</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_buffer">lex_buffer</span> : <code class="type">bytes</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_buffer_len">lex_buffer_len</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_abs_pos">lex_abs_pos</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_start_pos">lex_start_pos</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_curr_pos">lex_curr_pos</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_last_pos">lex_last_pos</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_last_action">lex_last_action</span> : <code class="type">int</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_eof_reached">lex_eof_reached</span> : <code class="type">bool</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_mem">lex_mem</span> : <code class="type">int array</code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_start_p">lex_start_p</span> : <code class="type"><a href="Lexing.html#TYPEposition">position</a></code>;</code></td> </tr> <tr> <td align="left" valign="top" > <code> </code></td> <td align="left" valign="top" > <code><span class="keyword">mutable </span><span id="TYPEELTlexbuf.lex_curr_p">lex_curr_p</span> : <code class="type"><a href="Lexing.html#TYPEposition">position</a></code>;</code></td> </tr></table> } <div class="info "> 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. <p> At each token, the lexing engine will copy <code class="code">lex_curr_p</code> to <code class="code">lex_start_p</code>, then change the <code class="code">pos_cnum</code> field of <code class="code">lex_curr_p</code> by updating it with the number of characters read since the start of the <code class="code">lexbuf</code>. 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 <code class="code">new_line</code>).<br> </div> <pre><span id="VALfrom_channel"><span class="keyword">val</span> from_channel</span> : <code class="type"><a href="Pervasives.html#TYPEin_channel">in_channel</a> -> <a href="Lexing.html#TYPElexbuf">lexbuf</a></code></pre><div class="info "> Create a lexer buffer on the given input channel. <code class="code"><span class="constructor">Lexing</span>.from_channel inchan</code> returns a lexer buffer which reads from the input channel <code class="code">inchan</code>, at the current reading position.<br> </div> <pre><span id="VALfrom_string"><span class="keyword">val</span> from_string</span> : <code class="type">string -> <a href="Lexing.html#TYPElexbuf">lexbuf</a></code></pre><div class="info "> 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.<br> </div> <pre><span id="VALfrom_function"><span class="keyword">val</span> from_function</span> : <code class="type">(bytes -> int -> int) -> <a href="Lexing.html#TYPElexbuf">lexbuf</a></code></pre><div class="info "> 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 byte sequence <code class="code">s</code> and a byte count <code class="code">n</code>. The function should put <code class="code">n</code> bytes or fewer in <code class="code">s</code>, starting at index 0, and return the number of bytes provided. A return value of 0 means end of input.<br> </div> <br> <h6 id="6_Functionsforlexersemanticactions">Functions for lexer semantic actions</h6><br> <br> 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 <code class="code">lexbuf</code>, which, in the code generated by <code class="code">ocamllex</code>, is bound to the lexer buffer passed to the parsing function.<br> <pre><span id="VALlexeme"><span class="keyword">val</span> lexeme</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> string</code></pre><div class="info "> <code class="code"><span class="constructor">Lexing</span>.lexeme lexbuf</code> returns the string matched by the regular expression.<br> </div> <pre><span id="VALlexeme_char"><span class="keyword">val</span> lexeme_char</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> int -> char</code></pre><div class="info "> <code class="code"><span class="constructor">Lexing</span>.lexeme_char lexbuf i</code> returns character number <code class="code">i</code> in the matched string.<br> </div> <pre><span id="VALlexeme_start"><span class="keyword">val</span> lexeme_start</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> int</code></pre><div class="info "> <code class="code"><span class="constructor">Lexing</span>.lexeme_start lexbuf</code> returns the offset in the input stream of the first character of the matched string. The first character of the stream has offset 0.<br> </div> <pre><span id="VALlexeme_end"><span class="keyword">val</span> lexeme_end</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> int</code></pre><div class="info "> <code class="code"><span class="constructor">Lexing</span>.lexeme_end lexbuf</code> 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.<br> </div> <pre><span id="VALlexeme_start_p"><span class="keyword">val</span> lexeme_start_p</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> <a href="Lexing.html#TYPEposition">position</a></code></pre><div class="info "> Like <code class="code">lexeme_start</code>, but return a complete <code class="code">position</code> instead of an offset.<br> </div> <pre><span id="VALlexeme_end_p"><span class="keyword">val</span> lexeme_end_p</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> <a href="Lexing.html#TYPEposition">position</a></code></pre><div class="info "> Like <code class="code">lexeme_end</code>, but return a complete <code class="code">position</code> instead of an offset.<br> </div> <pre><span id="VALnew_line"><span class="keyword">val</span> new_line</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> unit</code></pre><div class="info "> Update the <code class="code">lex_curr_p</code> 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.<br> <b>Since</b> 3.11.0<br> </div> <br> <h6 id="6_Miscellaneousfunctions">Miscellaneous functions</h6><br> <pre><span id="VALflush_input"><span class="keyword">val</span> flush_input</span> : <code class="type"><a href="Lexing.html#TYPElexbuf">lexbuf</a> -> unit</code></pre><div class="info "> Discard the contents of the buffer and reset the current position to 0. The next use of the lexbuf will trigger a refill.<br> </div> </body></html>