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<title>Unsafe/Coerce.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -XNoImplicitPrelude #-}</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 : Unsafe.Coerce</span>
<a name="line-5"></a><span class='hs-comment'>-- Copyright : Malcolm Wallace 2006</span>
<a name="line-6"></a><span class='hs-comment'>-- License : BSD-style (see the LICENSE file in the distribution)</span>
<a name="line-7"></a><span class='hs-comment'>--</span>
<a name="line-8"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</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 highly unsafe primitive 'unsafeCoerce' converts a value from any</span>
<a name="line-13"></a><span class='hs-comment'>-- type to any other type. Needless to say, if you use this function,</span>
<a name="line-14"></a><span class='hs-comment'>-- it is your responsibility to ensure that the old and new types have</span>
<a name="line-15"></a><span class='hs-comment'>-- identical internal representations, in order to prevent runtime corruption.</span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-- The types for which 'unsafeCoerce' is representation-safe may differ</span>
<a name="line-18"></a><span class='hs-comment'>-- from compiler to compiler (and version to version).</span>
<a name="line-19"></a><span class='hs-comment'>--</span>
<a name="line-20"></a><span class='hs-comment'>-- * Documentation for correct usage in GHC will be found under</span>
<a name="line-21"></a><span class='hs-comment'>-- 'unsafeCoerce#' in GHC.Base (around which 'unsafeCoerce' is just a</span>
<a name="line-22"></a><span class='hs-comment'>-- trivial wrapper).</span>
<a name="line-23"></a><span class='hs-comment'>--</span>
<a name="line-24"></a><span class='hs-comment'>-- * In nhc98, the only representation-safe coercions are between Enum</span>
<a name="line-25"></a><span class='hs-comment'>-- types with the same range (e.g. Int, Int32, Char, Word32),</span>
<a name="line-26"></a><span class='hs-comment'>-- or between a newtype and the type that it wraps.</span>
<a name="line-27"></a>
<a name="line-28"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Unsafe</span><span class='hs-varop'>.</span><span class='hs-conid'>Coerce</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafeCoerce</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-29"></a>
<a name="line-30"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__)</span>
<a name="line-31"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Prim</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafeCoerce</span><span class='hs-cpp'>#</span><span class='hs-layout'>)</span>
<a name="line-32"></a><a name="unsafeCoerce"></a><span class='hs-definition'>unsafeCoerce</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span>
<a name="line-33"></a><span class='hs-definition'>unsafeCoerce</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeCoerce</span><span class='hs-cpp'>#</span>
<a name="line-34"></a><span class='hs-cpp'>#endif</span>
<a name="line-35"></a>
<a name="line-36"></a><span class='hs-cpp'>#if defined(__NHC__)</span>
<a name="line-37"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>NonStdUnsafeCoerce</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafeCoerce</span><span class='hs-layout'>)</span>
<a name="line-38"></a><span class='hs-cpp'>#endif</span>
<a name="line-39"></a>
<a name="line-40"></a><span class='hs-cpp'>#if defined(__HUGS__)</span>
<a name="line-41"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hugs</span><span class='hs-varop'>.</span><span class='hs-conid'>IOExts</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafeCoerce</span><span class='hs-layout'>)</span>
<a name="line-42"></a><span class='hs-cpp'>#endif</span>
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