/usr/share/doc/libghc-parsec3-doc/html/Text-Parsec-Expr.html

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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Text-Parsec-Expr.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">parsec-3.1.11: Monadic parser combinators</p></div><div id="content"><div id="module-header"><table class="info"><tr><th valign="top">Copyright</th><td>(c) Daan Leijen 1999-2001 (c) Paolo Martini 2007</td></tr><tr><th>License</th><td>BSD-style (see the LICENSE file)</td></tr><tr><th>Maintainer</th><td>derek.a.elkins@gmail.com</td></tr><tr><th>Stability</th><td>provisional</td></tr><tr><th>Portability</th><td>non-portable</td></tr><tr><th>Safe Haskell</th><td>Safe</td></tr><tr><th>Language</th><td>Haskell98</td></tr></table><p class="caption">Text.Parsec.Expr</p></div><div id="description"><p class="caption">Description</p><div class="doc"><p>A helper module to parse &quot;expressions&quot;.
 Builds a parser given a table of operators and associativities.</p></div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">data</span> <a href="#t:Assoc">Assoc</a><ul class="subs"><li>= <a href="#v:AssocNone">AssocNone</a></li><li>| <a href="#v:AssocLeft">AssocLeft</a></li><li>| <a href="#v:AssocRight">AssocRight</a></li></ul></li><li class="src short"><span class="keyword">data</span> <a href="#t:Operator">Operator</a> s u m a<ul class="subs"><li>= <a href="#v:Infix">Infix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a -&gt; a)) <a href="Text-Parsec-Expr.html#t:Assoc">Assoc</a></li><li>| <a href="#v:Prefix">Prefix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a))</li><li>| <a href="#v:Postfix">Postfix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a))</li></ul></li><li class="src short"><span class="keyword">type</span> <a href="#t:OperatorTable">OperatorTable</a> s u m a = [[<a href="Text-Parsec-Expr.html#t:Operator">Operator</a> s u m a]]</li><li class="src short"><a href="#v:buildExpressionParser">buildExpressionParser</a> :: <a href="Text-Parsec.html#t:Stream">Stream</a> s m t =&gt; <a href="Text-Parsec-Expr.html#t:OperatorTable">OperatorTable</a> s u m a -&gt; <a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m a -&gt; <a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m a</li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><span class="keyword">data</span> <a id="t:Assoc" class="def">Assoc</a> <a href="src/Text-Parsec-Expr.html#Assoc" class="link">Source</a> <a href="#t:Assoc" class="selflink">#</a></p><div class="doc"><p>This data type specifies the associativity of operators: left, right
 or none.</p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a id="v:AssocNone" class="def">AssocNone</a></td><td class="doc empty">&nbsp;</td></tr><tr><td class="src"><a id="v:AssocLeft" class="def">AssocLeft</a></td><td class="doc empty">&nbsp;</td></tr><tr><td class="src"><a id="v:AssocRight" class="def">AssocRight</a></td><td class="doc empty">&nbsp;</td></tr></table></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a id="t:Operator" class="def">Operator</a> s u m a <a href="src/Text-Parsec-Expr.html#Operator" class="link">Source</a> <a href="#t:Operator" class="selflink">#</a></p><div class="doc"><p>This data type specifies operators that work on values of type <code>a</code>.
 An operator is either binary infix or unary prefix or postfix. A
 binary operator has also an associated associativity.</p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a id="v:Infix" class="def">Infix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a -&gt; a)) <a href="Text-Parsec-Expr.html#t:Assoc">Assoc</a></td><td class="doc empty">&nbsp;</td></tr><tr><td class="src"><a id="v:Prefix" class="def">Prefix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a))</td><td class="doc empty">&nbsp;</td></tr><tr><td class="src"><a id="v:Postfix" class="def">Postfix</a> (<a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m (a -&gt; a))</td><td class="doc empty">&nbsp;</td></tr></table></div></div><div class="top"><p class="src"><span class="keyword">type</span> <a id="t:OperatorTable" class="def">OperatorTable</a> s u m a = [[<a href="Text-Parsec-Expr.html#t:Operator">Operator</a> s u m a]] <a href="src/Text-Parsec-Expr.html#OperatorTable" class="link">Source</a> <a href="#t:OperatorTable" class="selflink">#</a></p><div class="doc"><p>An <code>OperatorTable s u m a</code> is a list of <code>Operator s u m a</code>
 lists. The list is ordered in descending
 precedence. All operators in one list have the same precedence (but
 may have a different associativity).</p></div></div><div class="top"><p class="src"><a id="v:buildExpressionParser" class="def">buildExpressionParser</a> :: <a href="Text-Parsec.html#t:Stream">Stream</a> s m t =&gt; <a href="Text-Parsec-Expr.html#t:OperatorTable">OperatorTable</a> s u m a -&gt; <a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m a -&gt; <a href="Text-Parsec.html#t:ParsecT">ParsecT</a> s u m a <a href="src/Text-Parsec-Expr.html#buildExpressionParser" class="link">Source</a> <a href="#v:buildExpressionParser" class="selflink">#</a></p><div class="doc"><p><code>buildExpressionParser table term</code> builds an expression parser for
 terms <code>term</code> with operators from <code>table</code>, taking the associativity
 and precedence specified in <code>table</code> into account. Prefix and postfix
 operators of the same precedence can only occur once (i.e. <code>--2</code> is
 not allowed if <code>-</code> is prefix negate). Prefix and postfix operators
 of the same precedence associate to the left (i.e. if <code>++</code> is
 postfix increment, than <code>-2++</code> equals <code>-1</code>, not <code>-3</code>).</p><p>The <code>buildExpressionParser</code> takes care of all the complexity
 involved in building expression parser. Here is an example of an
 expression parser that handles prefix signs, postfix increment and
 basic arithmetic.</p><pre> expr    = buildExpressionParser table term
         &lt;?&gt; &quot;expression&quot;

 term    =  parens expr 
         &lt;|&gt; natural
         &lt;?&gt; &quot;simple expression&quot;

 table   = [ [prefix &quot;-&quot; negate, prefix &quot;+&quot; id ]
           , [postfix &quot;++&quot; (+1)]
           , [binary &quot;*&quot; (*) AssocLeft, binary &quot;/&quot; (div) AssocLeft ]
           , [binary &quot;+&quot; (+) AssocLeft, binary &quot;-&quot; (-)   AssocLeft ]
           ]
         
 binary  name fun assoc = Infix (do{ reservedOp name; return fun }) assoc
 prefix  name fun       = Prefix (do{ reservedOp name; return fun })
 postfix name fun       = Postfix (do{ reservedOp name; return fun })</pre></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.17.3</p></div></body></html>
libghc-parsec3-doc 3.1.11-3build2 / usr / share / doc / libghc-parsec3-doc / html / Text-Parsec-Expr.html
