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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Data-Enumerator-Internal.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">enumerator-0.4.19: Reliable, high-performance processing with left-fold enumerators</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>jmillikin@gmail.com</td></tr><tr><th>Safe Haskell</th><td>None</td></tr></table><p class="caption">Data.Enumerator.Internal</p></div><div id="table-of-contents"><p class="caption">Contents</p><ul><li><a href="#g:1">Primitives
</a></li><li><a href="#g:2">Operators
</a></li><li><a href="#g:3">Miscellaneous
</a></li></ul></div><div id="description"><p class="caption">Description</p><div class="doc"><p>Core enumerator types, and some useful primitives.
</p><p>Be careful when using the functions defined in this module, as they will
allow you to create iteratees which violate the monad laws.
</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:Stream">Stream</a> a<ul class="subs"><li>= <a href="#v:Chunks">Chunks</a> [a] </li><li>| <a href="#v:EOF">EOF</a> </li></ul></li><li class="src short"><span class="keyword">newtype</span> <a href="#t:Iteratee">Iteratee</a> a m b = <a href="#v:Iteratee">Iteratee</a> {<ul class="subs"><li><a href="#v:runIteratee">runIteratee</a> :: m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)</li></ul>}</li><li class="src short"><span class="keyword">data</span> <a href="#t:Step">Step</a> a m b<ul class="subs"><li>= <a href="#v:Continue">Continue</a> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) </li><li>| <a href="#v:Yield">Yield</a> b (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a) </li><li>| <a href="#v:Error">Error</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Exception-Base.html#t:SomeException">SomeException</a> </li></ul></li><li class="src short"><span class="keyword">type</span> <a href="#t:Enumerator">Enumerator</a> a m b = <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b</li><li class="src short"><span class="keyword">type</span> <a href="#t:Enumeratee">Enumeratee</a> ao ai m b = <a href="Data-Enumerator-Internal.html#t:Step">Step</a> ai m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> ao m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> ai m b)</li><li class="src short"><a href="#v:returnI">returnI</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b</li><li class="src short"><a href="#v:continue">continue</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b</li><li class="src short"><a href="#v:yield">yield</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => b -> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b</li><li class="src short"><a href="#v:-62--62--61--61-">(>>==)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'</li><li class="src short"><a href="#v:-61--61--60--60-">(==<<)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'</li><li class="src short"><a href="#v:-36--36-">($$)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'</li><li class="src short"><a href="#v:-62--61--61--62-">(>==>)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'</li><li class="src short"><a href="#v:-60--61--61--60-">(<==<)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'</li><li class="src short"><a href="#v:enumEOF">enumEOF</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b</li><li class="src short"><a href="#v:checkContinue0">checkContinue0</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b</li><li class="src short"><a href="#v:checkContinue1">checkContinue1</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => ((s1 -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b) -> s1 -> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> s1 -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b</li><li class="src short"><a href="#v:checkDoneEx">checkDoneEx</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a' -> ((<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)) -> <a href="Data-Enumerator-Internal.html#t:Enumeratee">Enumeratee</a> a' a m b</li><li class="src short"><a href="#v:checkDone">checkDone</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => ((<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)) -> <a href="Data-Enumerator-Internal.html#t:Enumeratee">Enumeratee</a> a' a m b</li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:Stream" class="def">Stream</a> a <a href="src/Data-Enumerator-Internal.html#Stream" class="link">Source</a></p><div class="doc"><p>A <code><a href="Data-Enumerator-Internal.html#t:Stream">Stream</a></code> is a sequence of chunks generated by an <code><a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a></code>.
</p><p><code>(<code><a href="Data-Enumerator-Internal.html#v:Chunks">Chunks</a></code> [])</code> is used to indicate that a stream is still active, but
currently has no available data. Iteratees should ignore empty chunks.
</p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:Chunks" class="def">Chunks</a> [a]</td><td class="doc empty"> </td></tr><tr><td class="src"><a name="v:EOF" class="def">EOF</a></td><td class="doc empty"> </td></tr></table></div><div class="subs instances"><p id="control.i:Stream" class="caption collapser" onclick="toggleSection('i:Stream')">Instances</p><div id="section.i:Stream" class="show"><table><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Functor">Functor</a> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a></td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable1">Typeable1</a> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a></td><td class="doc"><p>Since: 0.4.8
</p></td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Applicative.html#t:Applicative">Applicative</a> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a></td><td class="doc"><p>Since: 0.4.5
</p></td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Eq.html#t:Eq">Eq</a> a => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Eq.html#t:Eq">Eq</a> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a)</td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Text-Show.html#t:Show">Show</a> a => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Text-Show.html#t:Show">Show</a> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a)</td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Monoid.html#t:Monoid">Monoid</a> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a)</td><td class="doc empty"> </td></tr></table></div></div></div><div class="top"><p class="src"><span class="keyword">newtype</span> <a name="t:Iteratee" class="def">Iteratee</a> a m b <a href="src/Data-Enumerator-Internal.html#Iteratee" class="link">Source</a></p><div class="doc"><p>The primary data type for this library; an iteratee consumes
chunks of input from a stream until it either yields a value or
encounters an error.
</p><p>Compatibility note: <code>Iteratee</code> will become abstract in <code>enumerator_0.5</code>. If
you depend on internal implementation details, please import
<code><a href="Data-Enumerator-Internal.html">Data.Enumerator.Internal</a></code>.
</p></div><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:Iteratee" class="def">Iteratee</a></td><td class="doc empty"> </td></tr><tr><td colspan="2"><div class="subs fields"><p class="caption">Fields</p><dl><dt class="src"><a name="v:runIteratee" class="def">runIteratee</a> :: m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)</dt><dd class="doc empty"> </dd></dl><div class="clear"></div></div></td></tr></table></div><div class="subs instances"><p id="control.i:Iteratee" class="caption collapser" onclick="toggleSection('i:Iteratee')">Instances</p><div id="section.i:Iteratee" class="show"><table><tr><td class="src"><a href="/usr/share/doc/libghc-transformers-doc/html/Control-Monad-Trans-Class.html#t:MonadTrans">MonadTrans</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a)</td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m)</td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Functor">Functor</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m)</td><td class="doc empty"> </td></tr><tr><td class="src">(<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable">Typeable</a> a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable1">Typeable1</a> m) => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable1">Typeable1</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m)</td><td class="doc"><p>Since: 0.4.6
</p></td></tr><tr><td class="src"><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Applicative.html#t:Applicative">Applicative</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m)</td><td class="doc empty"> </td></tr><tr><td class="src"><a href="/usr/share/doc/libghc-transformers-doc/html/Control-Monad-IO-Class.html#t:MonadIO">MonadIO</a> m => <a href="/usr/share/doc/libghc-transformers-doc/html/Control-Monad-IO-Class.html#t:MonadIO">MonadIO</a> (<a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m)</td><td class="doc empty"> </td></tr></table></div></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:Step" class="def">Step</a> a m b <a href="src/Data-Enumerator-Internal.html#Step" class="link">Source</a></p><div class="subs constructors"><p class="caption">Constructors</p><table><tr><td class="src"><a name="v:Continue" class="def">Continue</a> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b)</td><td class="doc"><p>The <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> is capable of accepting more input. Note that more input
is not necessarily required; the <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> might be able to generate a
value immediately if it receives <code><a href="Data-Enumerator-Internal.html#v:EOF">EOF</a></code>.
</p></td></tr><tr><td class="src"><a name="v:Yield" class="def">Yield</a> b (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a)</td><td class="doc"><p>The <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> cannot receive any more input, and has generated a
result. Included in this value is left-over input, which can be passed to
composed <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code>s.
</p></td></tr><tr><td class="src"><a name="v:Error" class="def">Error</a> <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Exception-Base.html#t:SomeException">SomeException</a></td><td class="doc"><p>The <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> encountered an error which prevents it from proceeding
further.
</p></td></tr></table></div><div class="subs instances"><p id="control.i:Step" class="caption collapser" onclick="toggleSection('i:Step')">Instances</p><div id="section.i:Step" class="show"><table><tr><td class="src">(<a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable">Typeable</a> a, <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable1">Typeable1</a> m) => <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Data-Typeable-Internal.html#t:Typeable1">Typeable1</a> (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m)</td><td class="doc"><p>Since: 0.4.8
</p></td></tr></table></div></div></div><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:Enumerator" class="def">Enumerator</a> a m b = <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b<a href="src/Data-Enumerator-Internal.html#Enumerator" class="link">Source</a></p><div class="doc"><p>Enumerators are sources of data, to be consumed by iteratees.
Enumerators typically read from an external source (parser, handle,
random generator, etc), then feed chunks into an tteratee until:
</p><ul><li> The input source runs out of data.
</li><li> The iteratee yields a result value.
</li><li> The iteratee throws an exception.
</li></ul></div></div><div class="top"><p class="src"><span class="keyword">type</span> <a name="t:Enumeratee" class="def">Enumeratee</a> ao ai m b = <a href="Data-Enumerator-Internal.html#t:Step">Step</a> ai m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> ao m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> ai m b)<a href="src/Data-Enumerator-Internal.html#Enumeratee" class="link">Source</a></p><div class="doc"><p>An enumeratee acts as a stream adapter; place one between an enumerator
and an iteratee, and it changes the type or contents of the input stream.
</p><p>Most users will want to combine enumerators, enumeratees, and iteratees
using the stream combinators <code>joinI</code> and <code>joinE</code>, or their operator aliases
<code>(=$)</code> and <code>($=)</code>. These combinators are used to manage how left-over input
is passed between elements of the data processing pipeline.
</p></div></div><h1 id="g:1">Primitives
</h1><div class="top"><p class="src"><a name="v:returnI" class="def">returnI</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b<a href="src/Data-Enumerator-Internal.html#returnI" class="link">Source</a></p><div class="doc"><pre><code><a href="Data-Enumerator-Internal.html#v:returnI">returnI</a></code> step = <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> (return step)</pre></div></div><div class="top"><p class="src"><a name="v:continue" class="def">continue</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b<a href="src/Data-Enumerator-Internal.html#continue" class="link">Source</a></p><div class="doc"><pre><code><a href="Data-Enumerator-Internal.html#v:continue">continue</a></code> k = <code><a href="Data-Enumerator-Internal.html#v:returnI">returnI</a></code> (<code><a href="Data-Enumerator-Internal.html#v:Continue">Continue</a></code> k)</pre></div></div><div class="top"><p class="src"><a name="v:yield" class="def">yield</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => b -> <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b<a href="src/Data-Enumerator-Internal.html#yield" class="link">Source</a></p><div class="doc"><pre><code><a href="Data-Enumerator-Internal.html#v:yield">yield</a></code> x extra = <code><a href="Data-Enumerator-Internal.html#v:returnI">returnI</a></code> (<code><a href="Data-Enumerator-Internal.html#v:Yield">Yield</a></code> x extra)</pre><p>WARNING: due to the current encoding of iteratees in this library,
careless use of the <code><a href="Data-Enumerator-Internal.html#v:yield">yield</a></code> primitive may violate the monad laws.
To prevent this, always make sure that an iteratee never yields
extra data unless it has received at least one input element.
</p><p>More strictly, iteratees may not yield data that they did not
receive as input. Don't use <code><a href="Data-Enumerator-Internal.html#v:yield">yield</a></code> to “inject” elements
into the stream.
</p></div></div><h1 id="g:2">Operators
</h1><div class="top"><p class="src"><a name="v:-62--62--61--61-" class="def">(>>==)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'<a href="src/Data-Enumerator-Internal.html#%3E%3E%3D%3D" class="link">Source</a></p><div class="doc"><p>The most primitive stream operator. <code>iter >>== enum</code> returns a new
iteratee which will read from <code>enum</code> before continuing.
</p></div></div><div class="top"><p class="src"><a name="v:-61--61--60--60-" class="def">(==<<)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'<a href="src/Data-Enumerator-Internal.html#%3D%3D%3C%3C" class="link">Source</a></p><div class="doc"><pre>(<code><a href="Data-Enumerator-Internal.html#v:-61--61--60--60-">==<<</a></code>) = flip (<code><a href="Data-Enumerator-Internal.html#v:-62--62--61--61-">>>==</a></code>)</pre></div></div><div class="top"><p class="src"><a name="v:-36--36-" class="def">($$)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'<a href="src/Data-Enumerator-Internal.html#%24%24" class="link">Source</a></p><div class="doc"><pre>(<code><a href="Data-Enumerator-Internal.html#v:-36--36-">$$</a></code>) = (<code><a href="Data-Enumerator-Internal.html#v:-61--61--60--60-">==<<</a></code>)</pre><p>This is somewhat easier to read when constructing an iteratee from many
processing stages. You can treat it like <code>(<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Prelude.html#v:-36-">$</a></code>)</code>, and read the data flow
from left to right.
</p><p>Since: 0.1.1
</p></div></div><div class="top"><p class="src"><a name="v:-62--61--61--62-" class="def">(>==>)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'<a href="src/Data-Enumerator-Internal.html#%3E%3D%3D%3E" class="link">Source</a></p><div class="doc"><pre>(<code><a href="Data-Enumerator-Internal.html#v:-62--61--61--62-">>==></a></code>) enum1 enum2 step = enum1 step <code><a href="Data-Enumerator-Internal.html#v:-62--62--61--61-">>>==</a></code> enum2</pre><p>The moral equivalent of <code>(<code><a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#v:-62--61--62-">>=></a></code>)</code> for iteratees.
</p><p>Since: 0.1.1
</p></div></div><div class="top"><p class="src"><a name="v:-60--61--61--60-" class="def">(<==<)</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b') -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m b'<a href="src/Data-Enumerator-Internal.html#%3C%3D%3D%3C" class="link">Source</a></p><div class="doc"><pre>(<code><a href="Data-Enumerator-Internal.html#v:-60--61--61--60-"><==<</a></code>) = flip (<code><a href="Data-Enumerator-Internal.html#v:-62--61--61--62-">>==></a></code>)</pre><p>Since: 0.1.1
</p></div></div><h1 id="g:3">Miscellaneous
</h1><div class="top"><p class="src"><a name="v:enumEOF" class="def">enumEOF</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b<a href="src/Data-Enumerator-Internal.html#enumEOF" class="link">Source</a></p><div class="doc"><p>Sends <code><a href="Data-Enumerator-Internal.html#v:EOF">EOF</a></code> to its iteratee. Most clients should use <code>run</code> or <code>run_</code>
instead.
</p></div></div><div class="top"><p class="src"><a name="v:checkContinue0" class="def">checkContinue0</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => (<a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b -> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b<a href="src/Data-Enumerator-Internal.html#checkContinue0" class="link">Source</a></p><div class="doc"><p>A common pattern in <code><a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a></code> implementations is to check whether
the inner <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> has finished, and if so, to return its output.
<code><a href="Data-Enumerator-Internal.html#v:checkContinue0">checkContinue0</a></code> passes its parameter a continuation if the <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code>
can still consume input; if not, it returns the iteratee's step.
</p><p>The type signature here is a bit crazy, but it's actually very easy to
use. Take this code:
</p><pre> repeat :: Monad m => a -> Enumerator a m b
repeat x = loop where
loop (Continue k) = k (Chunks [x]) >>== loop
loop step = returnI step
</pre><p>And rewrite it without the boilerplate:
</p><pre> repeat :: Monad m => a -> Enumerator a m b
repeat x = checkContinue0 $ \loop k -> k (Chunks [x] >>== loop
</pre><p>Since: 0.4.9
</p></div></div><div class="top"><p class="src"><a name="v:checkContinue1" class="def">checkContinue1</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => ((s1 -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b) -> s1 -> (<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> s1 -> <a href="Data-Enumerator-Internal.html#t:Enumerator">Enumerator</a> a m b<a href="src/Data-Enumerator-Internal.html#checkContinue1" class="link">Source</a></p><div class="doc"><p>Like <code><a href="Data-Enumerator-Internal.html#v:checkContinue0">checkContinue0</a></code>, but allows each loop step to use a state value:
</p><pre> iterate :: Monad m => (a -> a) -> a -> Enumerator a m b
iterate f = checkContinue1 $ \loop a k -> k (Chunks [a]) >>== loop (f a)
</pre><p>Since: 0.4.9
</p></div></div><div class="top"><p class="src"><a name="v:checkDoneEx" class="def">checkDoneEx</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => <a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a' -> ((<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)) -> <a href="Data-Enumerator-Internal.html#t:Enumeratee">Enumeratee</a> a' a m b<a href="src/Data-Enumerator-Internal.html#checkDoneEx" class="link">Source</a></p><div class="doc"><p>A common pattern in <code><a href="Data-Enumerator-Internal.html#t:Enumeratee">Enumeratee</a></code> implementations is to check whether
the inner <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code> has finished, and if so, to return its output.
<code><a href="Data-Enumerator-Internal.html#v:checkDone">checkDone</a></code> passes its parameter a continuation if the <code><a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a></code>
can still consume input, or yields otherwise.
</p><p>Since: 0.4.3
</p></div></div><div class="top"><p class="src"><a name="v:checkDone" class="def">checkDone</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/base-4.6.0.1/Control-Monad.html#t:Monad">Monad</a> m => ((<a href="Data-Enumerator-Internal.html#t:Stream">Stream</a> a -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a m b) -> <a href="Data-Enumerator-Internal.html#t:Iteratee">Iteratee</a> a' m (<a href="Data-Enumerator-Internal.html#t:Step">Step</a> a m b)) -> <a href="Data-Enumerator-Internal.html#t:Enumeratee">Enumeratee</a> a' a m b<a href="src/Data-Enumerator-Internal.html#checkDone" class="link">Source</a></p><div class="doc"><pre><code><a href="Data-Enumerator-Internal.html#v:checkDone">checkDone</a></code> = <code><a href="Data-Enumerator-Internal.html#v:checkDoneEx">checkDoneEx</a></code> (<code><a href="Data-Enumerator-Internal.html#v:Chunks">Chunks</a></code> [])</pre><p>Use this for enumeratees which do not have an input buffer.
</p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.13.2</p></div></body></html>
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