<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<!-- Generated by HsColour, http://code.haskell.org/~malcolm/hscolour/ -->
<title>Control/Arrow/Transformer/Stream.hs</title>
<link type='text/css' rel='stylesheet' href='hscolour.css' />
</head>
<body>
<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE FlexibleInstances, Rank2Types #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-4"></a><span class='hs-comment'>-- |</span>
<a name="line-5"></a><span class='hs-comment'>-- Module : Control.Arrow.Transformer.Stream</span>
<a name="line-6"></a><span class='hs-comment'>-- Copyright : (c) Ross Paterson 2003</span>
<a name="line-7"></a><span class='hs-comment'>-- License : BSD-style (see the LICENSE file in the distribution)</span>
<a name="line-8"></a><span class='hs-comment'>--</span>
<a name="line-9"></a><span class='hs-comment'>-- Maintainer : ross@soi.city.ac.uk</span>
<a name="line-10"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-11"></a><span class='hs-comment'>-- Portability : non-portable (multi-parameter type classes)</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- Arrow transformer lifting an arrow to streams.</span>
<a name="line-14"></a>
<a name="line-15"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Arrow</span><span class='hs-varop'>.</span><span class='hs-conid'>Transformer</span><span class='hs-varop'>.</span><span class='hs-conid'>Stream</span><span class='hs-layout'>(</span>
<a name="line-16"></a> <span class='hs-conid'>StreamArrow</span><span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-17"></a> <span class='hs-varid'>runStream</span><span class='hs-layout'>,</span>
<a name="line-18"></a> <span class='hs-conid'>StreamMap</span><span class='hs-layout'>,</span>
<a name="line-19"></a> <span class='hs-conid'>StreamMapST</span><span class='hs-layout'>,</span> <span class='hs-varid'>runStreamST</span><span class='hs-layout'>,</span>
<a name="line-20"></a> <span class='hs-conid'>ArrowAddStream</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-21"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-22"></a>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Arrow</span><span class='hs-varop'>.</span><span class='hs-conid'>Internals</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Arrow</span><span class='hs-varop'>.</span><span class='hs-conid'>Operations</span>
<a name="line-25"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Arrow</span><span class='hs-varop'>.</span><span class='hs-conid'>Transformer</span>
<a name="line-26"></a>
<a name="line-27"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Applicative</span>
<a name="line-28"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Arrow</span>
<a name="line-29"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Category</span>
<a name="line-30"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>ST</span>
<a name="line-31"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span>
<a name="line-32"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Stream</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-33"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Stream</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Stream</span>
<a name="line-34"></a>
<a name="line-35"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Prelude</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>id</span><span class='hs-layout'>,</span><span class='hs-layout'>(</span><span class='hs-varop'>.</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-36"></a>
<a name="line-37"></a><span class='hs-comment'>-- | Arrows between streams.</span>
<a name="line-38"></a><span class='hs-comment'>--</span>
<a name="line-39"></a><span class='hs-comment'>-- /Note/: 'lift' is only a functor if '***' in the underlying arrow is.</span>
<a name="line-40"></a>
<a name="line-41"></a><a name="StreamArrow"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-42"></a>
<a name="line-43"></a><a name="instance%20Category%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Category</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Category</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-44"></a> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>id</span>
<a name="line-45"></a> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>g</span><span class='hs-layout'>)</span>
<a name="line-46"></a>
<a name="line-47"></a><a name="instance%20Arrow%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Arrow</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-48"></a> <span class='hs-varid'>arr</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-49"></a> <span class='hs-varid'>first</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-50"></a> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>unzip</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>first</span> <span class='hs-varid'>f</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>uncurry</span> <span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>zip</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-51"></a>
<a name="line-52"></a><a name="genmap"></a><span class='hs-definition'>genmap</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span>
<a name="line-53"></a><span class='hs-definition'>genmap</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>xs</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>head</span> <span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>tail</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>></span>
<a name="line-54"></a> <span class='hs-varid'>f</span> <span class='hs-varop'>***</span> <span class='hs-varid'>genmap</span> <span class='hs-varid'>f</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>uncurry</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-conid'>Cons</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-55"></a>
<a name="line-56"></a><span class='hs-comment'>-- Caution: genmap is only a functor if *** for the base arrow is.</span>
<a name="line-57"></a><span class='hs-comment'>-- (For Kleisli arrows, that would mean a commutative monad.)</span>
<a name="line-58"></a><span class='hs-comment'>-- The same goes for the equivalent lift: it can be used to lift arrows,</span>
<a name="line-59"></a><span class='hs-comment'>-- but won't preserve composition unless *** does.</span>
<a name="line-60"></a>
<a name="line-61"></a><a name="instance%20ArrowTransformer%20(StreamArrow)%20a"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowTransformer</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>where</span>
<a name="line-62"></a> <span class='hs-varid'>lift</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>genmap</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-63"></a>
<a name="line-64"></a><span class='hs-comment'>-- The following promotions follow directly from the arrow transformer.</span>
<a name="line-65"></a>
<a name="line-66"></a><a name="instance%20ArrowZero%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowZero</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowZero</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-67"></a> <span class='hs-varid'>zeroArrow</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>zeroArrow</span>
<a name="line-68"></a>
<a name="line-69"></a><a name="instance%20ArrowState%20s%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowState</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowState</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-70"></a> <span class='hs-varid'>fetch</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>fetch</span>
<a name="line-71"></a> <span class='hs-varid'>store</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>store</span>
<a name="line-72"></a>
<a name="line-73"></a><a name="instance%20ArrowWriter%20w%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowWriter</span> <span class='hs-varid'>w</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowWriter</span> <span class='hs-varid'>w</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-74"></a> <span class='hs-varid'>write</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>write</span>
<a name="line-75"></a> <span class='hs-varid'>newWriter</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>newWriter</span> <span class='hs-varid'>f</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-varid'>strength</span><span class='hs-layout'>)</span>
<a name="line-76"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>strength</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Functor</span> <span class='hs-varid'>w'</span> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-varid'>w'</span> <span class='hs-varid'>a'</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>w'</span> <span class='hs-layout'>(</span><span class='hs-varid'>a'</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span>
<a name="line-77"></a> <span class='hs-varid'>strength</span> <span class='hs-layout'>(</span><span class='hs-varid'>v</span><span class='hs-layout'>,</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>x</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>v</span>
<a name="line-78"></a>
<a name="line-79"></a><span class='hs-comment'>-- liftings of standard classes</span>
<a name="line-80"></a>
<a name="line-81"></a><a name="instance%20ArrowChoice%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowChoice</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-82"></a> <span class='hs-varid'>left</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-83"></a> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>getLeft</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-varop'>&&&</span> <span class='hs-varid'>arr</span> <span class='hs-varid'>id</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-varid'>replace</span><span class='hs-layout'>)</span>
<a name="line-84"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>getLeft</span> <span class='hs-layout'>(</span><span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Cons</span> <span class='hs-varid'>x</span> <span class='hs-layout'>(</span><span class='hs-varid'>getLeft</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span>
<a name="line-85"></a> <span class='hs-varid'>getLeft</span> <span class='hs-layout'>(</span><span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>getLeft</span> <span class='hs-varid'>xs</span>
<a name="line-86"></a> <span class='hs-varid'>replace</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>~</span><span class='hs-layout'>(</span><span class='hs-conid'>Cons</span> <span class='hs-varid'>x</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-87"></a> <span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>replace</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-88"></a> <span class='hs-varid'>replace</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-89"></a> <span class='hs-conid'>Cons</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>replace</span> <span class='hs-layout'>(</span><span class='hs-varid'>xs</span><span class='hs-layout'>,</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-90"></a>
<a name="line-91"></a><a name="instance%20ArrowLoop%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowLoop</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowLoop</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-92"></a> <span class='hs-varid'>loop</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-93"></a> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>loop</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>uncurry</span> <span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>zip</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-conid'>Stream</span><span class='hs-varop'>.</span><span class='hs-varid'>unzip</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-94"></a>
<a name="line-95"></a><a name="instance%20ArrowPlus%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowPlus</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowPlus</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-96"></a> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span> <span class='hs-varop'><+></span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varop'><+></span> <span class='hs-varid'>g</span><span class='hs-layout'>)</span>
<a name="line-97"></a>
<a name="line-98"></a><span class='hs-comment'>-- I don't know of any other useful promotions.</span>
<a name="line-99"></a><span class='hs-comment'>-- (elimWriter can be promoted, but doesn't seem useful.)</span>
<a name="line-100"></a>
<a name="line-101"></a><span class='hs-comment'>-- Circuits</span>
<a name="line-102"></a>
<a name="line-103"></a><a name="instance%20ArrowCircuit%20(StreamArrow%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowLoop</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowCircuit</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-104"></a> <span class='hs-varid'>delay</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-conid'>Cons</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-105"></a>
<a name="line-106"></a><span class='hs-comment'>-- Other instances</span>
<a name="line-107"></a>
<a name="line-108"></a><a name="instance%20Functor%20(StreamArrow%20a%20b)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Functor</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-109"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>g</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-varid'>f</span>
<a name="line-110"></a>
<a name="line-111"></a><a name="instance%20Applicative%20(StreamArrow%20a%20b)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Arrow</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Applicative</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-112"></a> <span class='hs-varid'>pure</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>const</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-113"></a> <span class='hs-varid'>f</span> <span class='hs-varop'><*></span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varop'>&&&</span> <span class='hs-varid'>g</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>uncurry</span> <span class='hs-varid'>id</span><span class='hs-layout'>)</span>
<a name="line-114"></a>
<a name="line-115"></a><a name="instance%20Alternative%20(StreamArrow%20a%20b)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowPlus</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Alternative</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-116"></a> <span class='hs-varid'>empty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>zeroArrow</span>
<a name="line-117"></a> <span class='hs-varid'>f</span> <span class='hs-varop'><|></span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varop'><+></span> <span class='hs-varid'>g</span>
<a name="line-118"></a>
<a name="line-119"></a><a name="instance%20Monoid%20(StreamArrow%20a%20b%20c)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowPlus</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-120"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>zeroArrow</span>
<a name="line-121"></a> <span class='hs-varid'>mappend</span> <span class='hs-varid'>f</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span> <span class='hs-varop'><+></span> <span class='hs-varid'>g</span>
<a name="line-122"></a>
<a name="line-123"></a><span class='hs-comment'>-- | Run a stream processor on a stream of inputs, obtaining a stream</span>
<a name="line-124"></a><span class='hs-comment'>-- of outputs.</span>
<a name="line-125"></a><span class='hs-comment'>--</span>
<a name="line-126"></a><span class='hs-comment'>-- Typical usage in arrow notation:</span>
<a name="line-127"></a><span class='hs-comment'>--</span>
<a name="line-128"></a><span class='hs-comment'>-- > proc p -> do</span>
<a name="line-129"></a><span class='hs-comment'>-- > ...</span>
<a name="line-130"></a><span class='hs-comment'>-- > ys <- (|runStream (\x -> ...)|) xs</span>
<a name="line-131"></a><span class='hs-comment'>--</span>
<a name="line-132"></a><span class='hs-comment'>-- Here @xs@ refers to the input stream and @x@ to individual</span>
<a name="line-133"></a><span class='hs-comment'>-- elements of that stream. @ys@ is bound to the output stream.</span>
<a name="line-134"></a>
<a name="line-135"></a><a name="runStream"></a><span class='hs-definition'>runStream</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ArrowLoop</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span><span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>Stream</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span>
<a name="line-136"></a><span class='hs-definition'>runStream</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>x</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>e</span><span class='hs-layout'>,</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span>
<a name="line-137"></a>
<a name="line-138"></a><a name="instance%20ArrowAddStream%20(StreamArrow%20a)%20a"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowLoop</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowAddStream</span> <span class='hs-layout'>(</span><span class='hs-conid'>StreamArrow</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>where</span>
<a name="line-139"></a> <span class='hs-varid'>liftStream</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span>
<a name="line-140"></a> <span class='hs-varid'>elimStream</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runStream</span>
<a name="line-141"></a>
<a name="line-142"></a><a name="StreamMap"></a><span class='hs-comment'>-- | Mappings of streams</span>
<a name="line-143"></a><a name="StreamMap"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>StreamMap</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>-></span><span class='hs-layout'>)</span>
<a name="line-144"></a>
<a name="line-145"></a><span class='hs-comment'>-- | In-place state updates.</span>
<a name="line-146"></a><span class='hs-comment'>--</span>
<a name="line-147"></a><span class='hs-comment'>-- /Note/: this is an arrow type, and 'lift' can be used to promote arrows</span>
<a name="line-148"></a><span class='hs-comment'>-- from @'Kleisli' ('ST' s)@: the resulting arrow updates the state for</span>
<a name="line-149"></a><span class='hs-comment'>-- each stream element in turn, and as long as the final state in not</span>
<a name="line-150"></a><span class='hs-comment'>-- required all is well. However, 'lift' does not preserve composition,</span>
<a name="line-151"></a><span class='hs-comment'>-- because this monad isn't commutative. In particular, a composition</span>
<a name="line-152"></a><span class='hs-comment'>-- of 'lift's of state transformers will not work, as the second will</span>
<a name="line-153"></a><span class='hs-comment'>-- require the final state of the first.</span>
<a name="line-154"></a>
<a name="line-155"></a><a name="StreamMapST"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>StreamMapST</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-conid'>Kleisli</span> <span class='hs-layout'>(</span><span class='hs-conid'>ST</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-156"></a>
<a name="line-157"></a><span class='hs-comment'>-- | Encapsulate a local state.</span>
<a name="line-158"></a>
<a name="line-159"></a><a name="runStreamST"></a><span class='hs-definition'>runStreamST</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-keyword'>forall</span> <span class='hs-varid'>s</span><span class='hs-varop'>.</span> <span class='hs-conid'>StreamMapST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>e</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>StreamMap</span> <span class='hs-varid'>e</span> <span class='hs-varid'>c</span>
<a name="line-160"></a><span class='hs-definition'>runStreamST</span> <span class='hs-varid'>cf</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-varid'>input</span> <span class='hs-keyglyph'>-></span>
<a name="line-161"></a> <span class='hs-varid'>runST</span> <span class='hs-layout'>(</span><span class='hs-keyword'>let</span> <span class='hs-conid'>StreamArrow</span> <span class='hs-layout'>(</span><span class='hs-conid'>Kleisli</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>cf</span> <span class='hs-keyword'>in</span> <span class='hs-varid'>f</span> <span class='hs-varid'>input</span><span class='hs-layout'>)</span>
</pre></body>
</html>
distrib
>
Fedora
>
18
>
x86_64
>
media
>
updates
>
by-pkgid
>
765adc18ec52512b3512a9992c59746e
>
files
>
88
