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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">Cabal-1.14.0: A framework for packaging Haskell software</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Portability</th><td>portable</td></tr><tr><th>Maintainer</th><td>libraries@haskell.org</td></tr><tr><th>Safe Haskell</th><td>Safe-Infered</td></tr></table><p class="caption">Distribution.Compat.ReadP</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">The <code><a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a></code> type
</a></li><li><a href="#g:2">Primitive operations
</a></li><li><a href="#g:3">Other operations
</a></li><li><a href="#g:4">Running a parser
</a></li><li><a href="#g:5">Properties
</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>This is a library of parser combinators, originally written by Koen Claessen.
It parses all alternatives in parallel, so it never keeps hold of
the beginning of the input string, a common source of space leaks with
other parsers. The '(+++)' choice combinator is genuinely commutative;
it makes no difference which branch is "shorter".
</p><p>See also Koen's paper <em>Parallel Parsing Processes</em>
(<a href="http://www.cs.chalmers.se/~koen/publications.html">http://www.cs.chalmers.se/~koen/publications.html</a>).
</p><p>This version of ReadP has been locally hacked to make it H98, by
Martin Sjögren <a href="mailto:msjogren@gmail.com">mailto:msjogren@gmail.com</a>
</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">type</span> <a href="#t:ReadP">ReadP</a> r a = Parser r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> a</li><li class="src short"><a href="#v:get">get</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:look">look</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></li><li class="src short"><a href="#v:-43--43--43-">(+++)</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:-60--43--43-">(<++)</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> a a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:gather">gather</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> (<a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> P <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> r) a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (<a href="../base-4.5.1.0/Data-String.html#t:String">String</a>, a)</li><li class="src short"><a href="#v:pfail">pfail</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:satisfy">satisfy</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:char">char</a> :: <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></li><li class="src short"><a href="#v:string">string</a> :: <a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></li><li class="src short"><a href="#v:munch">munch</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></li><li class="src short"><a href="#v:munch1">munch1</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></li><li class="src short"><a href="#v:skipSpaces">skipSpaces</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</li><li class="src short"><a href="#v:choice">choice</a> :: [<a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a] -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:count">count</a> :: <a href="../base-4.5.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:between">between</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r open -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r close -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:option">option</a> :: a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:optional">optional</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</li><li class="src short"><a href="#v:many">many</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:many1">many1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:skipMany">skipMany</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</li><li class="src short"><a href="#v:skipMany1">skipMany1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</li><li class="src short"><a href="#v:sepBy">sepBy</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:sepBy1">sepBy1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:endBy">endBy</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:endBy1">endBy1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><a href="#v:chainr">chainr</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:chainl">chainl</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:chainl1">chainl1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:chainr1">chainr1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li><li class="src short"><a href="#v:manyTill">manyTill</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> [a] end -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</li><li class="src short"><span class="keyword">type</span> <a href="#t:ReadS">ReadS</a> a = <a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> [(a, <a href="../base-4.5.1.0/Data-String.html#t:String">String</a>)]</li><li class="src short"><a href="#v:readP_to_S">readP_to_S</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> a a -> <a href="Distribution-Compat-ReadP.html#t:ReadS">ReadS</a> a</li><li class="src short"><a href="#v:readS_to_P">readS_to_P</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadS">ReadS</a> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</li></ul></div><div id="interface"><h1 id="g:1">The <code><a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a></code> type
</h1><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:ReadP" class="def">ReadP</a> r a = Parser r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> a</p></div><h1 id="g:2">Primitive operations
</h1><div class="top"><p class="src"><a name="v:get" class="def">get</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></p><div class="doc"><p>Consumes and returns the next character.
Fails if there is no input left.
</p></div></div><div class="top"><p class="src"><a name="v:look" class="def">look</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></p><div class="doc"><p>Look-ahead: returns the part of the input that is left, without
consuming it.
</p></div></div><div class="top"><p class="src"><a name="v:-43--43--43-" class="def">(+++)</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Symmetric choice.
</p></div></div><div class="top"><p class="src"><a name="v:-60--43--43-" class="def">(<++)</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> a a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Local, exclusive, left-biased choice: If left parser
locally produces any result at all, then right parser is
not used.
</p></div></div><div class="top"><p class="src"><a name="v:gather" class="def">gather</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> (<a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> P <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> r) a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (<a href="../base-4.5.1.0/Data-String.html#t:String">String</a>, a)</p><div class="doc"><p>Transforms a parser into one that does the same, but
in addition returns the exact characters read.
IMPORTANT NOTE: <code><a href="Distribution-Compat-ReadP.html#v:gather">gather</a></code> gives a runtime error if its first argument
is built using any occurrences of readS_to_P.
</p></div></div><h1 id="g:3">Other operations
</h1><div class="top"><p class="src"><a name="v:pfail" class="def">pfail</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Always fails.
</p></div></div><div class="top"><p class="src"><a name="v:satisfy" class="def">satisfy</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></p><div class="doc"><p>Consumes and returns the next character, if it satisfies the
specified predicate.
</p></div></div><div class="top"><p class="src"><a name="v:char" class="def">char</a> :: <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a></p><div class="doc"><p>Parses and returns the specified character.
</p></div></div><div class="top"><p class="src"><a name="v:string" class="def">string</a> :: <a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></p><div class="doc"><p>Parses and returns the specified string.
</p></div></div><div class="top"><p class="src"><a name="v:munch" class="def">munch</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></p><div class="doc"><p>Parses the first zero or more characters satisfying the predicate.
</p></div></div><div class="top"><p class="src"><a name="v:munch1" class="def">munch1</a> :: (<a href="../base-4.5.1.0/Data-Char.html#t:Char">Char</a> -> <a href="../base-4.5.1.0/Data-Bool.html#t:Bool">Bool</a>) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r <a href="../base-4.5.1.0/Data-String.html#t:String">String</a></p><div class="doc"><p>Parses the first one or more characters satisfying the predicate.
</p></div></div><div class="top"><p class="src"><a name="v:skipSpaces" class="def">skipSpaces</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</p><div class="doc"><p>Skips all whitespace.
</p></div></div><div class="top"><p class="src"><a name="v:choice" class="def">choice</a> :: [<a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a] -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Combines all parsers in the specified list.
</p></div></div><div class="top"><p class="src"><a name="v:count" class="def">count</a> :: <a href="../base-4.5.1.0/Data-Int.html#t:Int">Int</a> -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code> count n p </code> parses <code>n</code> occurrences of <code>p</code> in sequence. A list of
results is returned.
</p></div></div><div class="top"><p class="src"><a name="v:between" class="def">between</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r open -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r close -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p><code> between open close p </code> parses <code>open</code>, followed by <code>p</code> and finally
<code>close</code>. Only the value of <code>p</code> is returned.
</p></div></div><div class="top"><p class="src"><a name="v:option" class="def">option</a> :: a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p><code>option x p</code> will either parse <code>p</code> or return <code>x</code> without consuming
any input.
</p></div></div><div class="top"><p class="src"><a name="v:optional" class="def">optional</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</p><div class="doc"><p><code>optional p</code> optionally parses <code>p</code> and always returns <code>()</code>.
</p></div></div><div class="top"><p class="src"><a name="v:many" class="def">many</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p>Parses zero or more occurrences of the given parser.
</p></div></div><div class="top"><p class="src"><a name="v:many1" class="def">many1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p>Parses one or more occurrences of the given parser.
</p></div></div><div class="top"><p class="src"><a name="v:skipMany" class="def">skipMany</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</p><div class="doc"><p>Like <code><a href="Distribution-Compat-ReadP.html#v:many">many</a></code>, but discards the result.
</p></div></div><div class="top"><p class="src"><a name="v:skipMany1" class="def">skipMany1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r ()</p><div class="doc"><p>Like <code><a href="Distribution-Compat-ReadP.html#v:many1">many1</a></code>, but discards the result.
</p></div></div><div class="top"><p class="src"><a name="v:sepBy" class="def">sepBy</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code>sepBy p sep</code> parses zero or more occurrences of <code>p</code>, separated by <code>sep</code>.
Returns a list of values returned by <code>p</code>.
</p></div></div><div class="top"><p class="src"><a name="v:sepBy1" class="def">sepBy1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code>sepBy1 p sep</code> parses one or more occurrences of <code>p</code>, separated by <code>sep</code>.
Returns a list of values returned by <code>p</code>.
</p></div></div><div class="top"><p class="src"><a name="v:endBy" class="def">endBy</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code>endBy p sep</code> parses zero or more occurrences of <code>p</code>, separated and ended
by <code>sep</code>.
</p></div></div><div class="top"><p class="src"><a name="v:endBy1" class="def">endBy1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r sep -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code>endBy p sep</code> parses one or more occurrences of <code>p</code>, separated and ended
by <code>sep</code>.
</p></div></div><div class="top"><p class="src"><a name="v:chainr" class="def">chainr</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p><code>chainr p op x</code> parses zero or more occurrences of <code>p</code>, separated by <code>op</code>.
Returns a value produced by a <em>right</em> associative application of all
functions returned by <code>op</code>. If there are no occurrences of <code>p</code>, <code>x</code> is
returned.
</p></div></div><div class="top"><p class="src"><a name="v:chainl" class="def">chainl</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p><code>chainl p op x</code> parses zero or more occurrences of <code>p</code>, separated by <code>op</code>.
Returns a value produced by a <em>left</em> associative application of all
functions returned by <code>op</code>. If there are no occurrences of <code>p</code>, <code>x</code> is
returned.
</p></div></div><div class="top"><p class="src"><a name="v:chainl1" class="def">chainl1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Like <code><a href="Distribution-Compat-ReadP.html#v:chainl">chainl</a></code>, but parses one or more occurrences of <code>p</code>.
</p></div></div><div class="top"><p class="src"><a name="v:chainr1" class="def">chainr1</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r (a -> a -> a) -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Like <code><a href="Distribution-Compat-ReadP.html#v:chainr">chainr</a></code>, but parses one or more occurrences of <code>p</code>.
</p></div></div><div class="top"><p class="src"><a name="v:manyTill" class="def">manyTill</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> [a] end -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r [a]</p><div class="doc"><p><code>manyTill p end</code> parses zero or more occurrences of <code>p</code>, until <code>end</code>
succeeds. Returns a list of values returned by <code>p</code>.
</p></div></div><h1 id="g:4">Running a parser
</h1><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:ReadS" class="def">ReadS</a> a = <a href="../base-4.5.1.0/Data-String.html#t:String">String</a> -> [(a, <a href="../base-4.5.1.0/Data-String.html#t:String">String</a>)]<a href="../base-4.5.1.0/src/Text-ParserCombinators-ReadP.html#ReadS" class="link">Source</a></p><div class="doc"><p>A parser for a type <code>a</code>, represented as a function that takes a
<code><a href="../base-4.5.1.0/Data-String.html#t:String">String</a></code> and returns a list of possible parses as <code>(a,<code><a href="../base-4.5.1.0/Data-String.html#t:String">String</a></code>)</code> pairs.
</p><p>Note that this kind of backtracking parser is very inefficient;
reading a large structure may be quite slow (cf <code><a href="../base-4.5.1.0/Text-ParserCombinators-ReadP.html#t:ReadP">ReadP</a></code>).
</p></div></div><div class="top"><p class="src"><a name="v:readP_to_S" class="def">readP_to_S</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> a a -> <a href="Distribution-Compat-ReadP.html#t:ReadS">ReadS</a> a</p><div class="doc"><p>Converts a parser into a Haskell ReadS-style function.
This is the main way in which you can "run" a <code><a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a></code> parser:
the expanded type is
<code> readP_to_S :: ReadP a -> String -> [(a,String)] </code>
</p></div></div><div class="top"><p class="src"><a name="v:readS_to_P" class="def">readS_to_P</a> :: <a href="Distribution-Compat-ReadP.html#t:ReadS">ReadS</a> a -> <a href="Distribution-Compat-ReadP.html#t:ReadP">ReadP</a> r a</p><div class="doc"><p>Converts a Haskell ReadS-style function into a parser.
Warning: This introduces local backtracking in the resulting
parser, and therefore a possible inefficiency.
</p></div></div><h1 id="g:5">Properties
</h1><div class="doc"><p>The following are QuickCheck specifications of what the combinators do.
These can be seen as formal specifications of the behavior of the
combinators.
</p><p>We use bags to give semantics to the combinators.
</p><pre> type Bag a = [a]
</pre><p>Equality on bags does not care about the order of elements.
</p><pre> (=~) :: Ord a => Bag a -> Bag a -> Bool
xs =~ ys = sort xs == sort ys
</pre><p>A special equality operator to avoid unresolved overloading
when testing the properties.
</p><pre> (=~.) :: Bag (Int,String) -> Bag (Int,String) -> Bool
(=~.) = (=~)
</pre><p>Here follow the properties:
</p><pre> prop_Get_Nil =
readP_to_S get [] =~ []
prop_Get_Cons c s =
readP_to_S get (c:s) =~ [(c,s)]
prop_Look s =
readP_to_S look s =~ [(s,s)]
prop_Fail s =
readP_to_S pfail s =~. []
prop_Return x s =
readP_to_S (return x) s =~. [(x,s)]
prop_Bind p k s =
readP_to_S (p >>= k) s =~.
[ ys''
| (x,s') <- readP_to_S p s
, ys'' <- readP_to_S (k (x::Int)) s'
]
prop_Plus p q s =
readP_to_S (p +++ q) s =~.
(readP_to_S p s ++ readP_to_S q s)
prop_LeftPlus p q s =
readP_to_S (p <++ q) s =~.
(readP_to_S p s +<+ readP_to_S q s)
where
[] +<+ ys = ys
xs +<+ _ = xs
prop_Gather s =
forAll readPWithoutReadS $ \p ->
readP_to_S (gather p) s =~
[ ((pre,x::Int),s')
| (x,s') <- readP_to_S p s
, let pre = take (length s - length s') s
]
prop_String_Yes this s =
readP_to_S (string this) (this ++ s) =~
[(this,s)]
prop_String_Maybe this s =
readP_to_S (string this) s =~
[(this, drop (length this) s) | this `isPrefixOf` s]
prop_Munch p s =
readP_to_S (munch p) s =~
[(takeWhile p s, dropWhile p s)]
prop_Munch1 p s =
readP_to_S (munch1 p) s =~
[(res,s') | let (res,s') = (takeWhile p s, dropWhile p s), not (null res)]
prop_Choice ps s =
readP_to_S (choice ps) s =~.
readP_to_S (foldr (+++) pfail ps) s
prop_ReadS r s =
readP_to_S (readS_to_P r) s =~. r s
</pre></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.11.0</p></div></body></html>
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