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<title>Control/Monad/Primitive.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE MagicHash, UnboxedTuples, TypeFamilies #-}</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'>-- Module : Control.Monad.Primitive</span>
<a name="line-5"></a><span class='hs-comment'>-- Copyright : (c) Roman Leshchinskiy 2009</span>
<a name="line-6"></a><span class='hs-comment'>-- License : BSD-style</span>
<a name="line-7"></a><span class='hs-comment'>--</span>
<a name="line-8"></a><span class='hs-comment'>-- Maintainer : Roman Leshchinskiy <rl@cse.unsw.edu.au></span>
<a name="line-9"></a><span class='hs-comment'>-- Portability : non-portable</span>
<a name="line-10"></a><span class='hs-comment'>-- </span>
<a name="line-11"></a><span class='hs-comment'>-- Primitive state-transformer monads</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a>
<a name="line-14"></a><span class='hs-keyword'>module</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'>Primitive</span> <span class='hs-layout'>(</span>
<a name="line-15"></a> <span class='hs-conid'>PrimMonad</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'>RealWorld</span><span class='hs-layout'>,</span> <span class='hs-varid'>primitive_</span><span class='hs-layout'>,</span>
<a name="line-16"></a> <span class='hs-varid'>primToPrim</span><span class='hs-layout'>,</span> <span class='hs-varid'>primToIO</span><span class='hs-layout'>,</span> <span class='hs-varid'>primToST</span><span class='hs-layout'>,</span>
<a name="line-17"></a> <span class='hs-varid'>unsafePrimToPrim</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafePrimToIO</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafePrimToST</span><span class='hs-layout'>,</span>
<a name="line-18"></a> <span class='hs-varid'>unsafeInlinePrim</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeInlineIO</span><span class='hs-layout'>,</span> <span class='hs-varid'>unsafeInlineST</span><span class='hs-layout'>,</span>
<a name="line-19"></a> <span class='hs-varid'>touch</span>
<a name="line-20"></a><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-21"></a>
<a name="line-22"></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-conid'>State</span><span class='hs-cpp'>#</span><span class='hs-layout'>,</span> <span class='hs-conid'>RealWorld</span><span class='hs-layout'>,</span> <span class='hs-varid'>touch</span><span class='hs-cpp'>#</span> <span class='hs-layout'>)</span>
<a name="line-23"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Base</span> <span class='hs-layout'>(</span> <span class='hs-varid'>unsafeCoerce</span><span class='hs-cpp'>#</span><span class='hs-layout'>,</span> <span class='hs-varid'>realWorld</span><span class='hs-cpp'>#</span> <span class='hs-layout'>)</span>
<a name="line-24"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>IOBase</span> <span class='hs-layout'>(</span> <span class='hs-conid'>IO</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span> <span class='hs-layout'>)</span>
<a name="line-25"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>ST</span> <span class='hs-layout'>(</span> <span class='hs-conid'>ST</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span> <span class='hs-layout'>)</span>
<a name="line-26"></a>
<a name="line-27"></a><a name="PrimMonad"></a><span class='hs-comment'>-- | Class of primitive state-transformer monads</span>
<a name="line-28"></a><a name="PrimMonad"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span>
<a name="line-29"></a> <span class='hs-comment'>-- | State token type</span>
<a name="line-30"></a> <span class='hs-keyword'>type</span> <span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span>
<a name="line-31"></a>
<a name="line-32"></a> <span class='hs-comment'>-- | Execute a primitive operation</span>
<a name="line-33"></a> <span class='hs-varid'>primitive</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-cpp'>#</span> <span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>a</span> <span class='hs-cpp'>#</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span>
<a name="line-34"></a>
<a name="line-35"></a>
<a name="line-36"></a> <span class='hs-comment'>-- | Expose the internal structure of the monad</span>
<a name="line-37"></a> <span class='hs-varid'>internal</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-cpp'>#</span> <span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>a</span> <span class='hs-cpp'>#</span><span class='hs-layout'>)</span>
<a name="line-38"></a>
<a name="line-39"></a><a name="primitive_"></a><span class='hs-comment'>-- | Execute a primitive operation with no result</span>
<a name="line-40"></a><span class='hs-definition'>primitive_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span>
<a name="line-41"></a> <span class='hs-keyglyph'>=></span> <span class='hs-layout'>(</span><span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>State</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span>
<a name="line-42"></a><span class='hs-comment'>{-# INLINE primitive_ #-}</span>
<a name="line-43"></a><span class='hs-definition'>primitive_</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>primitive</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span><span class='hs-cpp'>#</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-cpp'>#</span> <span class='hs-varid'>f</span> <span class='hs-varid'>s</span><span class='hs-cpp'>#</span><span class='hs-layout'>,</span> <span class='hs-conid'>()</span> <span class='hs-cpp'>#</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-44"></a>
<a name="line-45"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-conid'>IO</span> <span class='hs-keyword'>where</span>
<a name="line-46"></a> <span class='hs-keyword'>type</span> <span class='hs-conid'>PrimState</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>RealWorld</span>
<a name="line-47"></a> <span class='hs-varid'>primitive</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>IO</span>
<a name="line-48"></a> <span class='hs-varid'>internal</span> <span class='hs-layout'>(</span><span class='hs-conid'>IO</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>p</span>
<a name="line-49"></a>
<a name="line-50"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>PrimMonad</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-keyword'>where</span>
<a name="line-51"></a> <span class='hs-keyword'>type</span> <span class='hs-conid'>PrimState</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-keyglyph'>=</span> <span class='hs-varid'>s</span>
<a name="line-52"></a> <span class='hs-varid'>primitive</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>ST</span>
<a name="line-53"></a> <span class='hs-varid'>internal</span> <span class='hs-layout'>(</span><span class='hs-conid'>ST</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>p</span>
<a name="line-54"></a>
<a name="line-55"></a><a name="primToPrim"></a><span class='hs-comment'>-- | Convert a 'PrimMonad' to another monad with the same state token.</span>
<a name="line-56"></a><span class='hs-definition'>primToPrim</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m1</span><span class='hs-layout'>,</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m2</span><span class='hs-layout'>,</span> <span class='hs-conid'>PrimState</span> <span class='hs-varid'>m1</span> <span class='hs-keyglyph'>~</span> <span class='hs-conid'>PrimState</span> <span class='hs-varid'>m2</span><span class='hs-layout'>)</span>
<a name="line-57"></a> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m1</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m2</span> <span class='hs-varid'>a</span>
<a name="line-58"></a><span class='hs-definition'>primToPrim</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>primitive</span> <span class='hs-layout'>(</span><span class='hs-varid'>internal</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-59"></a>
<a name="line-60"></a><a name="primToIO"></a><span class='hs-comment'>-- | Convert a 'PrimMonad' with a 'RealWorld' state token to 'IO'</span>
<a name="line-61"></a><span class='hs-definition'>primToIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>~</span> <span class='hs-conid'>RealWorld</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-62"></a><span class='hs-definition'>primToIO</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>primToPrim</span>
<a name="line-63"></a>
<a name="line-64"></a><a name="primToST"></a><span class='hs-comment'>-- | Convert a 'PrimMonad' to 'ST'</span>
<a name="line-65"></a><span class='hs-definition'>primToST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimState</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span>
<a name="line-66"></a><span class='hs-definition'>primToST</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>primToPrim</span>
<a name="line-67"></a>
<a name="line-68"></a><a name="unsafePrimToPrim"></a><span class='hs-comment'>-- | Convert a 'PrimMonad' to another monad with a possibly different state</span>
<a name="line-69"></a><span class='hs-comment'>-- token. This operation is highly unsafe!</span>
<a name="line-70"></a><span class='hs-definition'>unsafePrimToPrim</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m1</span><span class='hs-layout'>,</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m1</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m2</span> <span class='hs-varid'>a</span>
<a name="line-71"></a><span class='hs-definition'>unsafePrimToPrim</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>primitive</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafeCoerce</span><span class='hs-cpp'>#</span> <span class='hs-layout'>(</span><span class='hs-varid'>internal</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-72"></a>
<a name="line-73"></a><a name="unsafePrimToST"></a><span class='hs-comment'>-- | Convert any 'PrimMonad' to 'ST' with an arbitrary state token. This</span>
<a name="line-74"></a><span class='hs-comment'>-- operations is highly unsafe!</span>
<a name="line-75"></a><span class='hs-definition'>unsafePrimToST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span>
<a name="line-76"></a><span class='hs-definition'>unsafePrimToST</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePrimToPrim</span>
<a name="line-77"></a>
<a name="line-78"></a><a name="unsafePrimToIO"></a><span class='hs-comment'>-- | Convert any 'PrimMonad' to 'IO'. This operation is highly unsafe!</span>
<a name="line-79"></a><span class='hs-definition'>unsafePrimToIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-80"></a><span class='hs-definition'>unsafePrimToIO</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePrimToPrim</span>
<a name="line-81"></a>
<a name="line-82"></a><a name="unsafeInlinePrim"></a><span class='hs-definition'>unsafeInlinePrim</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-83"></a><span class='hs-comment'>{-# INLINE unsafeInlinePrim #-}</span>
<a name="line-84"></a><span class='hs-definition'>unsafeInlinePrim</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeInlineIO</span> <span class='hs-layout'>(</span><span class='hs-varid'>unsafePrimToIO</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-85"></a>
<a name="line-86"></a><a name="unsafeInlineIO"></a><span class='hs-definition'>unsafeInlineIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-87"></a><span class='hs-comment'>{-# INLINE unsafeInlineIO #-}</span>
<a name="line-88"></a><span class='hs-definition'>unsafeInlineIO</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>internal</span> <span class='hs-varid'>m</span> <span class='hs-varid'>realWorld</span><span class='hs-cpp'>#</span> <span class='hs-keyword'>of</span> <span class='hs-layout'>(</span><span class='hs-cpp'>#</span> <span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>r</span> <span class='hs-cpp'>#</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>r</span>
<a name="line-89"></a>
<a name="line-90"></a><a name="unsafeInlineST"></a><span class='hs-definition'>unsafeInlineST</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ST</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-91"></a><span class='hs-comment'>{-# INLINE unsafeInlineST #-}</span>
<a name="line-92"></a><span class='hs-definition'>unsafeInlineST</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafeInlinePrim</span>
<a name="line-93"></a>
<a name="line-94"></a><a name="touch"></a><span class='hs-definition'>touch</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PrimMonad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-conid'>()</span>
<a name="line-95"></a><span class='hs-definition'>touch</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unsafePrimToPrim</span>
<a name="line-96"></a> <span class='hs-varop'>$</span> <span class='hs-layout'>(</span><span class='hs-varid'>primitive</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>touch</span><span class='hs-cpp'>#</span> <span class='hs-varid'>x</span> <span class='hs-varid'>s</span> <span class='hs-keyword'>of</span> <span class='hs-layout'>{</span> <span class='hs-varid'>s'</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-cpp'>#</span> <span class='hs-varid'>s'</span><span class='hs-layout'>,</span> <span class='hs-conid'>()</span> <span class='hs-cpp'>#</span><span class='hs-layout'>)</span> <span class='hs-layout'>}</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>
<a name="line-97"></a>
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