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<title>Batteries user guide : BatGenlex</title>
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<h1>Module <a href="type_BatGenlex.html">BatGenlex</a></h1>
<pre><span class="keyword">module</span> BatGenlex: <code class="code"><span class="keyword">sig</span></code> <a href="BatGenlex.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top">
A generic lexical analyzer.
<p>
This module implements a simple ``standard'' lexical analyzer, presented
as a function from character streams to token streams. It implements
roughly the lexical conventions of OCaml, but is parameterized by the
set of keywords of your language.
<p>
Example: a lexer suitable for a desk calculator is obtained by
<pre class="codepre"><code class="code"> <span class="keyword">let</span> lexer = make_lexer [<span class="string">"+"</span>;<span class="string">"-"</span>;<span class="string">"*"</span>;<span class="string">"/"</span>;<span class="string">"let"</span>;<span class="string">"="</span>; <span class="string">"("</span>; <span class="string">")"</span>] </code></pre>
<p>
The associated parser would be a function from <code class="code">token stream</code>
to, for instance, <code class="code">int</code>, and would have rules such as:
<p>
<pre class="codepre"><code class="code"> <span class="keyword">let</span> parse_expr = <span class="keyword">parser</span><br>
[< <span class="keywordsign">'</span><span class="constructor">Int</span> n >] <span class="keywordsign">-></span> n<br>
<span class="keywordsign">|</span> [< <span class="keywordsign">'</span><span class="constructor">Kwd</span> <span class="string">"("</span>; n = parse_expr; <span class="keywordsign">'</span><span class="constructor">Kwd</span> <span class="string">")"</span> >] <span class="keywordsign">-></span> n<br>
<span class="keywordsign">|</span> [< n1 = parse_expr; n2 = parse_remainder n1 >] <span class="keywordsign">-></span> n2<br>
<span class="keyword">and</span> parse_remainder n1 = <span class="keyword">parser</span><br>
[< <span class="keywordsign">'</span><span class="constructor">Kwd</span> <span class="string">"+"</span>; n2 = parse_expr >] <span class="keywordsign">-></span> n1+n2<br>
<span class="keywordsign">|</span> ...<br>
</code></pre><br>
<b>Author(s):</b> Jacques Garrigue, David Teller<br>
</div>
<hr width="100%">
<pre><span id="TYPEtoken"><span class="keyword">type</span> <code class="type"></code>token</span> = <code class="type">Genlex.token</code> = </pre><table class="typetable">
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.Kwd"><span class="constructor">Kwd</span></span> <span class="keyword">of</span> <code class="type">string</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.Ident"><span class="constructor">Ident</span></span> <span class="keyword">of</span> <code class="type">string</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.Int"><span class="constructor">Int</span></span> <span class="keyword">of</span> <code class="type">int</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.Float"><span class="constructor">Float</span></span> <span class="keyword">of</span> <code class="type">float</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.String"><span class="constructor">String</span></span> <span class="keyword">of</span> <code class="type">string</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTtoken.Char"><span class="constructor">Char</span></span> <span class="keyword">of</span> <code class="type">char</code></code></td>
</tr></table>
<div class="info ">
The type of tokens. The lexical classes are: <code class="code"><span class="constructor">Int</span></code> and <code class="code"><span class="constructor">Float</span></code>
for integer and floating-point numbers; <code class="code"><span class="constructor">String</span></code> for
string literals, enclosed in double quotes; <code class="code"><span class="constructor">Char</span></code> for
character literals, enclosed in single quotes; <code class="code"><span class="constructor">Ident</span></code> for
identifiers (either sequences of letters, digits, underscores
and quotes, or sequences of ``operator characters'' such as
<code class="code">+</code>, <code class="code">*</code>, etc); and <code class="code"><span class="constructor">Kwd</span></code> for keywords (either identifiers or
single ``special characters'' such as <code class="code">(</code>, <code class="code">}</code>, etc).<br>
</div>
<pre><span id="VALmake_lexer"><span class="keyword">val</span> make_lexer</span> : <code class="type">string list -> char Stream.t -> <a href="BatGenlex.html#TYPEtoken">token</a> Stream.t</code></pre><div class="info ">
Construct the lexer function. The first argument is the list of
keywords. An identifier <code class="code">s</code> is returned as <code class="code"><span class="constructor">Kwd</span> s</code> if <code class="code">s</code>
belongs to this list, and as <code class="code"><span class="constructor">Ident</span> s</code> otherwise.
A special character <code class="code">s</code> is returned as <code class="code"><span class="constructor">Kwd</span> s</code> if <code class="code">s</code>
belongs to this list, and cause a lexical error (exception
<code class="code"><span class="constructor">Parse_error</span></code>) otherwise. Blanks and newlines are skipped.
Comments delimited by <code class="code">(*</code> and <code class="code">*)</code> are skipped as well,
and can be nested.<br>
</div>
<pre><code><span id="TYPElexer_error"><span class="keyword">type</span> <code class="type"></code>lexer_error</span> = </code></pre><table class="typetable">
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTlexer_error.IllegalCharacter"><span class="constructor">IllegalCharacter</span></span> <span class="keyword">of</span> <code class="type">char</code></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTlexer_error.NotReallyAChar"><span class="constructor">NotReallyAChar</span></span></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTlexer_error.NotReallyAnEscape"><span class="constructor">NotReallyAnEscape</span></span></code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code><span class="keyword">|</span></code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTlexer_error.EndOfStream"><span class="constructor">EndOfStream</span></span></code></td>
</tr></table>
<pre><span id="EXCEPTIONLexerError"><span class="keyword">exception</span> LexerError</span> <span class="keyword">of</span> <code class="type"><a href="BatGenlex.html#TYPElexer_error">lexer_error</a> * int</code></pre>
<pre><span id="TYPEt"><span class="keyword">type</span> <code class="type"></code>t</span> </pre>
<div class="info ">
A lexer<br>
</div>
<pre><span id="VALof_list"><span class="keyword">val</span> of_list</span> : <code class="type">string list -> <a href="BatGenlex.html#TYPEt">t</a></code></pre><div class="info ">
Create a lexer from a list of keywords<br>
</div>
<pre><span id="VALto_stream_filter"><span class="keyword">val</span> to_stream_filter</span> : <code class="type"><a href="BatGenlex.html#TYPEt">t</a> -> char Stream.t -> <a href="BatGenlex.html#TYPEtoken">token</a> Stream.t</code></pre><div class="info ">
Apply the lexer to a stream.<br>
</div>
<pre><span id="VALto_enum_filter"><span class="keyword">val</span> to_enum_filter</span> : <code class="type"><a href="BatGenlex.html#TYPEt">t</a> -> char <a href="BatEnum.html#TYPEt">BatEnum.t</a> -> <a href="BatGenlex.html#TYPEtoken">token</a> <a href="BatEnum.html#TYPEt">BatEnum.t</a></code></pre><div class="info ">
Apply the lexer to an enum.<br>
</div>
<pre><span id="VALto_lazy_list_filter"><span class="keyword">val</span> to_lazy_list_filter</span> : <code class="type"><a href="BatGenlex.html#TYPEt">t</a> -> char <a href="BatLazyList.html#TYPEt">BatLazyList.t</a> -> <a href="BatGenlex.html#TYPEtoken">token</a> <a href="BatLazyList.html#TYPEt">BatLazyList.t</a></code></pre><div class="info ">
Apply the lexer to a lazy list.<br>
</div>
<pre><span id="VALstring_of_token"><span class="keyword">val</span> string_of_token</span> : <code class="type"><a href="BatGenlex.html#TYPEtoken">token</a> -> string</code></pre><br>
<h6 id="6_Extendingtootherlanguages">Extending to other languages</h6><br>
<pre><span class="keyword">module</span> <a href="BatGenlex.Languages.html">Languages</a>: <code class="code"><span class="keyword">sig</span></code> <a href="BatGenlex.Languages.html">..</a> <code class="code"><span class="keyword">end</span></code></pre></body></html>
