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<title>Control/Arrow/Transformer/Reader.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE FlexibleInstances #-}</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.Reader</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 that adds a read-only state (i.e. an environment).</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'>Reader</span><span class='hs-layout'>(</span>
<a name="line-16"></a> <span class='hs-conid'>ReaderArrow</span><span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-17"></a> <span class='hs-varid'>runReader</span><span class='hs-layout'>,</span>
<a name="line-18"></a> <span class='hs-conid'>ArrowAddReader</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span>
<a name="line-19"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-20"></a>
<a name="line-21"></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-22"></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-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'>Transformer</span>
<a name="line-24"></a>
<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'>Applicative</span>
<a name="line-26"></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-27"></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-28"></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-29"></a>
<a name="line-30"></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-31"></a>
<a name="line-32"></a><span class='hs-comment'>-- | An arrow type that augments an existing arrow with a read-only state</span>
<a name="line-33"></a><span class='hs-comment'>-- (or environment). The 'ArrowReader' class contains the operations</span>
<a name="line-34"></a><span class='hs-comment'>-- on this state.</span>
<a name="line-35"></a>
<a name="line-36"></a><a name="ReaderArrow"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</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'>ReaderArrow</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> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span>
<a name="line-37"></a>
<a name="line-38"></a><span class='hs-comment'>-- | Encapsulation of a state-reading computation, taking a value for the</span>
<a name="line-39"></a><span class='hs-comment'>-- state.</span>
<a name="line-40"></a><span class='hs-comment'>--</span>
<a name="line-41"></a><span class='hs-comment'>-- Typical usage in arrow notation:</span>
<a name="line-42"></a><span class='hs-comment'>--</span>
<a name="line-43"></a><span class='hs-comment'>-- > proc p -> ...</span>
<a name="line-44"></a><span class='hs-comment'>-- > (|runReader cmd|) env</span>
<a name="line-45"></a>
<a name="line-46"></a><a name="runReader"></a><span class='hs-definition'>runReader</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-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span> <span class='hs-varid'>e</span> <span class='hs-varid'>b</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-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-varid'>b</span>
<a name="line-47"></a><span class='hs-definition'>runReader</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f</span>
<a name="line-48"></a>
<a name="line-49"></a><span class='hs-comment'>-- arrow transformer</span>
<a name="line-50"></a>
<a name="line-51"></a><a name="instance%20ArrowTransformer%20(ReaderArrow%20r)%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'>ReaderArrow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>where</span>
<a name="line-52"></a> <span class='hs-varid'>lift</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>fst</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-53"></a>
<a name="line-54"></a><span class='hs-comment'>-- liftings of standard classes</span>
<a name="line-55"></a>
<a name="line-56"></a><a name="instance%20Category%20(ReaderArrow%20r%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'>Category</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-57"></a> <span class='hs-varid'>id</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>fst</span><span class='hs-layout'>)</span>
<a name="line-58"></a> <span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span>
<a name="line-59"></a> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>first</span> <span class='hs-varid'>g</span> <span class='hs-varop'>.</span> <span class='hs-varid'>arr</span> <span class='hs-varid'>dupenv</span><span class='hs-layout'>)</span>
<a name="line-60"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>dupenv</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-61"></a>
<a name="line-62"></a><a name="instance%20Arrow%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-63"></a> <span class='hs-varid'>arr</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fst</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-64"></a> <span class='hs-varid'>first</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>first</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-65"></a>
<a name="line-66"></a><a name="swapsnd"></a><span class='hs-definition'>swapsnd</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</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-layout'>(</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><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-67"></a><span class='hs-definition'>swapsnd</span> <span class='hs-keyglyph'>~</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>~</span><span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</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-layout'>(</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><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-68"></a>
<a name="line-69"></a><a name="instance%20ArrowChoice%20(ReaderArrow%20r%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowChoice</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'>ReaderArrow</span> <span class='hs-varid'>r</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'>left</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>dist'</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>left</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-71"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>dist'</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Either</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-varid'>c</span>
<a name="line-72"></a> <span class='hs-varid'>dist'</span> <span class='hs-layout'>(</span><span class='hs-conid'>Left</span> <span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Left</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-73"></a> <span class='hs-varid'>dist'</span> <span class='hs-layout'>(</span><span class='hs-conid'>Right</span> <span class='hs-varid'>c</span><span class='hs-layout'>,</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Right</span> <span class='hs-varid'>c</span>
<a name="line-74"></a>
<a name="line-75"></a><a name="instance%20ArrowApply%20(ReaderArrow%20r%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowApply</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowApply</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-76"></a> <span class='hs-varid'>app</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span>
<a name="line-77"></a> <span class='hs-layout'>(</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-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>,</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>app</span><span class='hs-layout'>)</span>
<a name="line-78"></a>
<a name="line-79"></a><a name="instance%20ArrowZero%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-80"></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-81"></a>
<a name="line-82"></a><a name="instance%20ArrowPlus%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-83"></a> <span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span> <span class='hs-varop'><+></span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>g</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</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-84"></a>
<a name="line-85"></a><a name="instance%20ArrowLoop%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-86"></a> <span class='hs-varid'>loop</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</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-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-87"></a>
<a name="line-88"></a><span class='hs-comment'>-- new instances</span>
<a name="line-89"></a>
<a name="line-90"></a><a name="instance%20ArrowReader%20r%20(ReaderArrow%20r%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'>ArrowReader</span> <span class='hs-varid'>r</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-91"></a> <span class='hs-varid'>readState</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>snd</span><span class='hs-layout'>)</span>
<a name="line-92"></a> <span class='hs-varid'>newReader</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>fst</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-93"></a>
<a name="line-94"></a><a name="instance%20ArrowAddReader%20r%20(ReaderArrow%20r%20a)%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'>ArrowAddReader</span> <span class='hs-varid'>r</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</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-95"></a> <span class='hs-varid'>liftReader</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span>
<a name="line-96"></a> <span class='hs-varid'>elimReader</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>runReader</span>
<a name="line-97"></a>
<a name="line-98"></a><span class='hs-comment'>-- liftings of other classes</span>
<a name="line-99"></a>
<a name="line-100"></a><a name="instance%20ArrowCircuit%20(ReaderArrow%20r%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowCircuit</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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-101"></a> <span class='hs-varid'>delay</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-layout'>(</span><span class='hs-varid'>delay</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-102"></a>
<a name="line-103"></a><a name="instance%20ArrowError%20ex%20(ReaderArrow%20r%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowError</span> <span class='hs-varid'>ex</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowError</span> <span class='hs-varid'>ex</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</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'>raise</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lift</span> <span class='hs-varid'>raise</span>
<a name="line-105"></a> <span class='hs-varid'>handle</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>handle</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-106"></a> <span class='hs-varid'>tryInUnless</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-107"></a> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>tryInUnless</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-108"></a> <span class='hs-varid'>newError</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>newError</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-109"></a>
<a name="line-110"></a><a name="instance%20ArrowState%20s%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-111"></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-112"></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-113"></a>
<a name="line-114"></a><a name="instance%20ArrowWriter%20s%20(ReaderArrow%20r%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowWriter</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ArrowWriter</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-115"></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-116"></a> <span class='hs-varid'>newWriter</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>newWriter</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-117"></a>
<a name="line-118"></a><span class='hs-comment'>-- Promotions of encapsulation operators.</span>
<a name="line-119"></a>
<a name="line-120"></a><a name="instance%20ArrowAddError%20ex%20(ReaderArrow%20r%20a)%20(ReaderArrow%20r%20a')"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowAddError</span> <span class='hs-varid'>ex</span> <span class='hs-varid'>a</span> <span class='hs-varid'>a'</span> <span class='hs-keyglyph'>=></span>
<a name="line-121"></a> <span class='hs-conid'>ArrowAddError</span> <span class='hs-varid'>ex</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a'</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-122"></a> <span class='hs-varid'>liftError</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftError</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-123"></a> <span class='hs-varid'>elimError</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-124"></a> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>elimError</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>h</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-125"></a>
<a name="line-126"></a><a name="instance%20ArrowAddState%20s%20(ReaderArrow%20r%20a)%20(ReaderArrow%20r%20a')"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowAddState</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>a'</span> <span class='hs-keyglyph'>=></span>
<a name="line-127"></a> <span class='hs-conid'>ArrowAddState</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a'</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-128"></a> <span class='hs-varid'>liftState</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftState</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-129"></a> <span class='hs-varid'>elimState</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>arr</span> <span class='hs-varid'>swapsnd</span> <span class='hs-varop'>>>></span> <span class='hs-varid'>elimState</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-130"></a>
<a name="line-131"></a><span class='hs-comment'>-- instance ArrowAddReader r a a' =></span>
<a name="line-132"></a><span class='hs-comment'>-- ArrowAddReader r (ReaderArrow r a) (ReaderArrow r a') where</span>
<a name="line-133"></a><span class='hs-comment'>-- elimReader (ReaderArrow f) = ReaderArrow (arr swapsnd >>> elimReader f)</span>
<a name="line-134"></a>
<a name="line-135"></a><a name="instance%20ArrowAddWriter%20s%20(ReaderArrow%20r%20a)%20(ReaderArrow%20r%20a')"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>ArrowAddWriter</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-varid'>a'</span> <span class='hs-keyglyph'>=></span>
<a name="line-136"></a> <span class='hs-conid'>ArrowAddWriter</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>r</span> <span class='hs-varid'>a'</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-137"></a> <span class='hs-varid'>liftWriter</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>liftWriter</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-138"></a> <span class='hs-varid'>elimWriter</span> <span class='hs-layout'>(</span><span class='hs-conid'>ReaderArrow</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ReaderArrow</span> <span class='hs-layout'>(</span><span class='hs-varid'>elimWriter</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span>
<a name="line-139"></a>
<a name="line-140"></a><span class='hs-comment'>-- Other instances</span>
<a name="line-141"></a>
<a name="line-142"></a><a name="instance%20Functor%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</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-143"></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-144"></a>
<a name="line-145"></a><a name="instance%20Applicative%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</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-146"></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-147"></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-148"></a>
<a name="line-149"></a><a name="instance%20Alternative%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</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-150"></a> <span class='hs-varid'>empty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>zeroArrow</span>
<a name="line-151"></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-152"></a>
<a name="line-153"></a><a name="instance%20Monoid%20(ReaderArrow%20r%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'>ReaderArrow</span> <span class='hs-varid'>r</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-154"></a> <span class='hs-varid'>mempty</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>zeroArrow</span>
<a name="line-155"></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>
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