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<title>src/ForSyDe/AbsentExt.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE TemplateHaskell, DeriveDataTypeable #-}</span>
<a name="line-2"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-3"></a><span class='hs-comment'>-- |</span>
<a name="line-4"></a><span class='hs-comment'>-- Module : ForSyDe.AbsentExt</span>
<a name="line-5"></a><span class='hs-comment'>-- Copyright : (c) SAM Group, KTH/ICT/ECS 2007-2008</span>
<a name="line-6"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span>
<a name="line-7"></a><span class='hs-comment'>-- </span>
<a name="line-8"></a><span class='hs-comment'>-- Maintainer : forsyde-dev@ict.kth.se</span>
<a name="line-9"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-10"></a><span class='hs-comment'>-- Portability : portable</span>
<a name="line-11"></a><span class='hs-comment'>--</span>
<a name="line-12"></a><span class='hs-comment'>-- The 'AbstExt' is used to extend existing data types with the value</span>
<a name="line-13"></a><span class='hs-comment'>-- \'absent\', which models the absence of a value.</span>
<a name="line-14"></a><span class='hs-comment'>-- </span>
<a name="line-15"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-16"></a>
<a name="line-17"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>ForSyDe</span><span class='hs-varop'>.</span><span class='hs-conid'>AbsentExt</span><span class='hs-layout'>(</span>
<a name="line-18"></a> <span class='hs-conid'>AbstExt</span> <span class='hs-layout'>(</span><span class='hs-conid'>Abst</span><span class='hs-layout'>,</span> <span class='hs-conid'>Prst</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>fromAbstExt</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeFromAbstExt</span><span class='hs-layout'>,</span>
<a name="line-19"></a> <span class='hs-varid'>abstExt</span><span class='hs-layout'>,</span> <span class='hs-varid'>psi</span><span class='hs-layout'>,</span>
<a name="line-20"></a> <span class='hs-varid'>isAbsent</span><span class='hs-layout'>,</span> <span class='hs-varid'>isPresent</span><span class='hs-layout'>,</span> <span class='hs-varid'>abstExtFunc</span><span class='hs-layout'>)</span>
<a name="line-21"></a> <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'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Data</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Language</span><span class='hs-varop'>.</span><span class='hs-conid'>Haskell</span><span class='hs-varop'>.</span><span class='hs-conid'>TH</span><span class='hs-varop'>.</span><span class='hs-conid'>Lift</span>
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<a name="line-27"></a><a name="AbstExt"></a><span class='hs-comment'>-- |The data type 'AbstExt' has two constructors. The constructor 'Abst' is used to model the absence of a value, while the constructor 'Prst' is used to model present values.</span>
<a name="line-28"></a><a name="AbstExt"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Abst</span>
<a name="line-29"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Prst</span> <span class='hs-varid'>a</span>
<a name="line-30"></a> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span><span class='hs-layout'>,</span> <span class='hs-conid'>Data</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable</span><span class='hs-layout'>)</span>
<a name="line-31"></a><span class='hs-varop'>$</span><span class='hs-layout'>(</span><span class='hs-varid'>deriveLift1</span> <span class='hs-chr'>'</span><span class='hs-chr'>'</span><span class='hs-conid'>AbstExt</span><span class='hs-layout'>)</span>
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<a name="line-35"></a><a name="fromAbstExt"></a><span class='hs-comment'>-- |The function 'fromAbstExt' extracts the inner value contained in 'AbstExt'</span>
<a name="line-36"></a><span class='hs-definition'>fromAbstExt</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-comment'>-- ^ Default value returned if the input is 'Abst' </span>
<a name="line-37"></a> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-38"></a><a name="unsafeFromAbstExt"></a><span class='hs-comment'>-- |Similar to 'fromAbstExt', but without default value</span>
<a name="line-39"></a><span class='hs-definition'>unsafeFromAbstExt</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-40"></a><a name="isPresent"></a><span class='hs-comment'>-- |The functions 'isPresent' checks for the presence of a value.</span>
<a name="line-41"></a><span class='hs-definition'>isPresent</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-42"></a><a name="isAbsent"></a><span class='hs-comment'>-- |The functions 'isAbsent' checks for the absence of a value.</span>
<a name="line-43"></a><span class='hs-definition'>isAbsent</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-44"></a><a name="abstExtFunc"></a><span class='hs-comment'>-- |The function 'abstExtFunc' extends a function in order to process absent extended values. If the input is (\"bottom\"), the output will also be (\"bottom\").</span>
<a name="line-45"></a><span class='hs-definition'>abstExtFunc</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>b</span>
<a name="line-46"></a><a name="psi"></a><span class='hs-comment'>-- | The function 'psi' is identical to 'abstExtFunc' and should be used in future.</span>
<a name="line-47"></a><span class='hs-definition'>psi</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>b</span>
<a name="line-48"></a><a name="abstExt"></a><span class='hs-comment'>-- | The function 'abstExt' converts a usual value to a present value. </span>
<a name="line-49"></a><span class='hs-definition'>abstExt</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span>
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<a name="line-56"></a><span class='hs-comment'>-- Implementation of Library Functions</span>
<a name="line-57"></a>
<a name="line-58"></a><span class='hs-comment'>-- | The data type 'AbstExt' is defined as an instance of 'Show' and 'Read'. \'_\' represents the value 'Abst' while a present value is represented with its value, e.g. 'Prst' 1 is represented as \'1\'.</span>
<a name="line-59"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Show</span> <span class='hs-layout'>(</span><span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-60"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showsAbstExt</span> <span class='hs-varid'>x</span>
<a name="line-61"></a>
<a name="line-62"></a><a name="showsAbstExt"></a><span class='hs-definition'>showsAbstExt</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Show</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Char</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Char</span><span class='hs-keyglyph'>]</span>
<a name="line-63"></a><span class='hs-definition'>showsAbstExt</span> <span class='hs-conid'>Abst</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varop'>++</span><span class='hs-layout'>)</span> <span class='hs-str'>"_"</span>
<a name="line-64"></a><span class='hs-definition'>showsAbstExt</span> <span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varop'>++</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>show</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
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<a name="line-66"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Read</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Read</span> <span class='hs-layout'>(</span><span class='hs-conid'>AbstExt</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'>readsPrec</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>readsAbstExt</span> <span class='hs-varid'>x</span>
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<a name="line-69"></a><a name="readsAbstExt"></a><span class='hs-definition'>readsAbstExt</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Read</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>ReadS</span> <span class='hs-layout'>(</span><span class='hs-conid'>AbstExt</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-70"></a><span class='hs-definition'>readsAbstExt</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-conid'>Abst</span><span class='hs-layout'>,</span> <span class='hs-varid'>r1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-layout'>(</span><span class='hs-str'>"_"</span><span class='hs-layout'>,</span> <span class='hs-varid'>r1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lex</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</span>
<a name="line-71"></a> <span class='hs-varop'>++</span> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>r2</span><span class='hs-layout'>)</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'>r2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>reads</span> <span class='hs-varid'>s</span><span class='hs-keyglyph'>]</span>
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<a name="line-73"></a><span class='hs-definition'>abstExt</span> <span class='hs-varid'>v</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Prst</span> <span class='hs-varid'>v</span>
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<a name="line-75"></a><span class='hs-definition'>fromAbstExt</span> <span class='hs-varid'>x</span> <span class='hs-conid'>Abst</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-76"></a><span class='hs-definition'>fromAbstExt</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>y</span>
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<a name="line-78"></a><span class='hs-definition'>unsafeFromAbstExt</span> <span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-79"></a><span class='hs-definition'>unsafeFromAbstExt</span> <span class='hs-conid'>Abst</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>error</span> <span class='hs-str'>"AbsentExt.unsafeFromAbstExt: Abst"</span>
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<a name="line-81"></a><span class='hs-definition'>isPresent</span> <span class='hs-conid'>Abst</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-82"></a><span class='hs-definition'>isPresent</span> <span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
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<a name="line-84"></a><span class='hs-definition'>isAbsent</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>not</span> <span class='hs-varop'>.</span> <span class='hs-varid'>isPresent</span>
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<a name="line-86"></a><span class='hs-definition'>abstExtFunc</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>f'</span>
<a name="line-87"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>f'</span> <span class='hs-conid'>Abst</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Abst</span>
<a name="line-88"></a> <span class='hs-varid'>f'</span> <span class='hs-layout'>(</span><span class='hs-conid'>Prst</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Prst</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
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<a name="line-91"></a><span class='hs-definition'>psi</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>abstExtFunc</span>
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