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<title>Control/Monad/Random/Class.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE MultiParamTypeClasses, UndecidableInstances, FunctionalDependencies #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>{- |
<a name="line-4"></a>Copyright : 2006-2007 Cale Gibbard, Russell O'Connor, Dan Doel, Remi Turk, Eric Kidd.
<a name="line-5"></a>License : OtherLicense
<a name="line-6"></a>Stability : experimental
<a name="line-7"></a>Portability : non-portable (multi-parameter type classes, undecidable instances)
<a name="line-8"></a>
<a name="line-9"></a>A type class for random number generation monads. See
<a name="line-10"></a><<a href="http://www.haskell.org/haskellwiki/NewMonads/MonadRandom">http://www.haskell.org/haskellwiki/NewMonads/MonadRandom</a>> for the original
<a name="line-11"></a>version of this code.
<a name="line-12"></a>
<a name="line-13"></a>Instances of this type class include 'Control.Monad.Random.Rand' and
<a name="line-14"></a>monads created using 'Control.Monad.Random.RandT'.
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<a name="line-16"></a>-}</span>
<a name="line-17"></a>
<a name="line-18"></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'>Random</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <span class='hs-layout'>(</span>
<a name="line-19"></a> <span class='hs-conid'>MonadRandom</span><span class='hs-layout'>,</span>
<a name="line-20"></a> <span class='hs-varid'>getRandom</span><span class='hs-layout'>,</span>
<a name="line-21"></a> <span class='hs-varid'>getRandomR</span><span class='hs-layout'>,</span>
<a name="line-22"></a> <span class='hs-varid'>getRandoms</span><span class='hs-layout'>,</span>
<a name="line-23"></a> <span class='hs-varid'>getRandomRs</span><span class='hs-layout'>,</span>
<a name="line-24"></a> <span class='hs-conid'>MonadSplit</span><span class='hs-layout'>,</span>
<a name="line-25"></a> <span class='hs-varid'>getSplit</span>
<a name="line-26"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-27"></a>
<a name="line-28"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Random</span>
<a name="line-29"></a>
<a name="line-30"></a><a name="MonadRandom"></a><span class='hs-comment'>-- | An interface to random number generation monads.</span>
<a name="line-31"></a><a name="MonadRandom"></a><span class='hs-keyword'>class</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadRandom</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span>
<a name="line-32"></a> <span class='hs-comment'>-- | Return a randomly-selected value of type @a@. See</span>
<a name="line-33"></a> <span class='hs-comment'>-- 'System.Random.random' for details.</span>
<a name="line-34"></a> <span class='hs-varid'>getRandom</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Random</span> <span class='hs-varid'>a</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-35"></a> <span class='hs-comment'>-- | Return an infinite stream of random values of type @a@. See</span>
<a name="line-36"></a> <span class='hs-comment'>-- 'System.Random.randoms' for details.</span>
<a name="line-37"></a> <span class='hs-varid'>getRandoms</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Random</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span>
<a name="line-38"></a> <span class='hs-comment'>-- | Return a randomly-selected value of type @a@ in the range</span>
<a name="line-39"></a> <span class='hs-comment'>-- /(lo,hi)/. See 'System.Random.randomR' for details.</span>
<a name="line-40"></a> <span class='hs-varid'>getRandomR</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Random</span> <span class='hs-varid'>a</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'>a</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-41"></a> <span class='hs-comment'>-- | Return an infinite stream of randomly-selected value of type @a@</span>
<a name="line-42"></a> <span class='hs-comment'>-- in the range /(lo,hi)/. See 'System.Random.randomRs' for details.</span>
<a name="line-43"></a> <span class='hs-varid'>getRandomRs</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Random</span> <span class='hs-varid'>a</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'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span>
<a name="line-44"></a>
<a name="line-45"></a><a name="MonadSplit"></a><span class='hs-comment'>-- | An interface to monads with splittable state (as most random number generation monads will have).</span>
<a name="line-46"></a><a name="MonadSplit"></a><span class='hs-comment'>-- The intention is that the 'getSplit' action splits the state, returning one half of the result, and</span>
<a name="line-47"></a><a name="MonadSplit"></a><span class='hs-comment'>-- setting the new state to the other.</span>
<a name="line-48"></a><a name="MonadSplit"></a><span class='hs-keyword'>class</span> <span class='hs-layout'>(</span><span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>MonadSplit</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span> <span class='hs-keyword'>where</span>
<a name="line-49"></a> <span class='hs-varid'>getSplit</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span>
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