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<pre><a name="line-1"></a><span class='comment'>-- ------------------------------------------------------------</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='comment'>{- |
<a name="line-4"></a> Module : Control.Arrow.ArrowIO
<a name="line-5"></a> Copyright : Copyright (C) 2005 Uwe Schmidt
<a name="line-6"></a> License : MIT
<a name="line-7"></a>
<a name="line-8"></a> Maintainer : Uwe Schmidt (uwe\@fh-wedel.de)
<a name="line-9"></a> Stability : experimental
<a name="line-10"></a> Portability: portable
<a name="line-11"></a> Version : $Id: ArrowIO.hs,v 1.6 2005/09/02 17:09:39 hxml Exp $
<a name="line-12"></a>
<a name="line-13"></a>Lifting of IO actions to arrows
<a name="line-14"></a>
<a name="line-15"></a>-}</span>
<a name="line-16"></a>
<a name="line-17"></a><span class='comment'>-- ------------------------------------------------------------</span>
<a name="line-18"></a>
<a name="line-19"></a><span class='keyword'>module</span> <span class='conid'>Control</span><span class='varop'>.</span><span class='conid'>Arrow</span><span class='varop'>.</span><span class='conid'>ArrowIO</span>
<a name="line-20"></a> <span class='layout'>(</span> <span class='conid'>ArrowIO</span><span class='layout'>(</span><span class='keyglyph'>..</span><span class='layout'>)</span>
<a name="line-21"></a> <span class='layout'>,</span> <span class='conid'>ArrowIOIf</span><span class='layout'>(</span><span class='keyglyph'>..</span><span class='layout'>)</span>
<a name="line-22"></a> <span class='layout'>)</span>
<a name="line-23"></a><span class='keyword'>where</span>
<a name="line-24"></a>
<a name="line-25"></a><span class='keyword'>import</span> <span class='conid'>Control</span><span class='varop'>.</span><span class='conid'>Arrow</span>
<a name="line-26"></a>
<a name="line-27"></a><span class='comment'>-- | the interface for converting an IO action into an arrow</span>
<a name="line-28"></a>
<a name="line-29"></a><a name="ArrowIO"></a><span class='keyword'>class</span> <span class='conid'>Arrow</span> <span class='varid'>a</span> <span class='keyglyph'>=></span> <span class='conid'>ArrowIO</span> <span class='varid'>a</span> <span class='keyword'>where</span>
<a name="line-30"></a>
<a name="line-31"></a> <span class='comment'>-- | construct an arrow from an IO action</span>
<a name="line-32"></a> <span class='varid'>arrIO</span> <span class='keyglyph'>::</span> <span class='layout'>(</span><span class='varid'>b</span> <span class='keyglyph'>-></span> <span class='conid'>IO</span> <span class='varid'>c</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='varid'>b</span> <span class='varid'>c</span>
<a name="line-33"></a>
<a name="line-34"></a> <span class='comment'>-- | construct an arrow from an IO action without any parameter</span>
<a name="line-35"></a> <span class='varid'>arrIO0</span> <span class='keyglyph'>::</span> <span class='conid'>IO</span> <span class='varid'>c</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='varid'>b</span> <span class='varid'>c</span>
<a name="line-36"></a> <span class='varid'>arrIO0</span> <span class='varid'>f</span> <span class='keyglyph'>=</span> <span class='varid'>arrIO</span> <span class='layout'>(</span><span class='varid'>const</span> <span class='varid'>f</span><span class='layout'>)</span>
<a name="line-37"></a>
<a name="line-38"></a> <span class='comment'>-- | construction of a 2 argument arrow from a binary IO action</span>
<a name="line-39"></a> <span class='comment'>-- |</span>
<a name="line-40"></a> <span class='comment'>-- | example: @ a1 &&& a2 >>> arr2 f @</span>
<a name="line-41"></a>
<a name="line-42"></a> <span class='varid'>arrIO2</span> <span class='keyglyph'>::</span> <span class='layout'>(</span><span class='varid'>b1</span> <span class='keyglyph'>-></span> <span class='varid'>b2</span> <span class='keyglyph'>-></span> <span class='conid'>IO</span> <span class='varid'>c</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='layout'>(</span><span class='varid'>b1</span><span class='layout'>,</span> <span class='varid'>b2</span><span class='layout'>)</span> <span class='varid'>c</span>
<a name="line-43"></a> <span class='varid'>arrIO2</span> <span class='varid'>f</span> <span class='keyglyph'>=</span> <span class='varid'>arrIO</span> <span class='layout'>(</span><span class='keyglyph'>\</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x1</span><span class='layout'>,</span> <span class='varid'>x2</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>f</span> <span class='varid'>x1</span> <span class='varid'>x2</span><span class='layout'>)</span>
<a name="line-44"></a>
<a name="line-45"></a> <span class='comment'>-- | construction of a 3 argument arrow from a 3-ary IO action</span>
<a name="line-46"></a> <span class='comment'>-- |</span>
<a name="line-47"></a> <span class='comment'>-- | example: @ a1 &&& a2 &&& a3 >>> arr3 f @</span>
<a name="line-48"></a>
<a name="line-49"></a> <span class='varid'>arrIO3</span> <span class='keyglyph'>::</span> <span class='layout'>(</span><span class='varid'>b1</span> <span class='keyglyph'>-></span> <span class='varid'>b2</span> <span class='keyglyph'>-></span> <span class='varid'>b3</span> <span class='keyglyph'>-></span> <span class='conid'>IO</span> <span class='varid'>c</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='layout'>(</span><span class='varid'>b1</span><span class='layout'>,</span> <span class='layout'>(</span><span class='varid'>b2</span><span class='layout'>,</span> <span class='varid'>b3</span><span class='layout'>)</span><span class='layout'>)</span> <span class='varid'>c</span>
<a name="line-50"></a> <span class='varid'>arrIO3</span> <span class='varid'>f</span> <span class='keyglyph'>=</span> <span class='varid'>arrIO</span> <span class='layout'>(</span><span class='keyglyph'>\</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x1</span><span class='layout'>,</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x2</span><span class='layout'>,</span> <span class='varid'>x3</span><span class='layout'>)</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>f</span> <span class='varid'>x1</span> <span class='varid'>x2</span> <span class='varid'>x3</span><span class='layout'>)</span>
<a name="line-51"></a>
<a name="line-52"></a> <span class='comment'>-- | construction of a 4 argument arrow from a 4-ary IO action</span>
<a name="line-53"></a> <span class='comment'>-- |</span>
<a name="line-54"></a> <span class='comment'>-- | example: @ a1 &&& a2 &&& a3 &&& a4 >>> arr4 f @</span>
<a name="line-55"></a>
<a name="line-56"></a> <span class='varid'>arrIO4</span> <span class='keyglyph'>::</span> <span class='layout'>(</span><span class='varid'>b1</span> <span class='keyglyph'>-></span> <span class='varid'>b2</span> <span class='keyglyph'>-></span> <span class='varid'>b3</span> <span class='keyglyph'>-></span> <span class='varid'>b4</span> <span class='keyglyph'>-></span> <span class='conid'>IO</span> <span class='varid'>c</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='layout'>(</span><span class='varid'>b1</span><span class='layout'>,</span> <span class='layout'>(</span><span class='varid'>b2</span><span class='layout'>,</span> <span class='layout'>(</span><span class='varid'>b3</span><span class='layout'>,</span> <span class='varid'>b4</span><span class='layout'>)</span><span class='layout'>)</span><span class='layout'>)</span> <span class='varid'>c</span>
<a name="line-57"></a> <span class='varid'>arrIO4</span> <span class='varid'>f</span> <span class='keyglyph'>=</span> <span class='varid'>arrIO</span> <span class='layout'>(</span><span class='keyglyph'>\</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x1</span><span class='layout'>,</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x2</span><span class='layout'>,</span> <span class='keyglyph'>~</span><span class='layout'>(</span><span class='varid'>x3</span><span class='layout'>,</span> <span class='varid'>x4</span><span class='layout'>)</span><span class='layout'>)</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>f</span> <span class='varid'>x1</span> <span class='varid'>x2</span> <span class='varid'>x3</span> <span class='varid'>x4</span><span class='layout'>)</span>
<a name="line-58"></a>
<a name="line-59"></a>
<a name="line-60"></a><span class='comment'>-- | the interface for converting an IO predicate into a list arrow</span>
<a name="line-61"></a>
<a name="line-62"></a><a name="ArrowIOIf"></a><span class='keyword'>class</span> <span class='layout'>(</span><span class='conid'>Arrow</span> <span class='varid'>a</span><span class='layout'>,</span> <span class='conid'>ArrowIO</span> <span class='varid'>a</span><span class='layout'>)</span> <span class='keyglyph'>=></span> <span class='conid'>ArrowIOIf</span> <span class='varid'>a</span> <span class='keyword'>where</span>
<a name="line-63"></a>
<a name="line-64"></a> <span class='comment'>-- | builds an arrow from an IO predicate</span>
<a name="line-65"></a> <span class='comment'>--</span>
<a name="line-66"></a> <span class='comment'>-- if the predicate holds, the single list containing the input is returned, else the empty list,</span>
<a name="line-67"></a> <span class='comment'>-- similar to 'Control.Arrow.ArrowList.isA'</span>
<a name="line-68"></a>
<a name="line-69"></a> <span class='varid'>isIOA</span> <span class='keyglyph'>::</span> <span class='layout'>(</span><span class='varid'>b</span> <span class='keyglyph'>-></span> <span class='conid'>IO</span> <span class='conid'>Bool</span><span class='layout'>)</span> <span class='keyglyph'>-></span> <span class='varid'>a</span> <span class='varid'>b</span> <span class='varid'>b</span>
<a name="line-70"></a>
<a name="line-71"></a><span class='comment'>-- ------------------------------------------------------------</span>
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