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23 lines
599 B
Haskell
23 lines
599 B
Haskell
{-# LANGUAGE FlexibleContexts #-}
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module Tests.NonDetEff where
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import Control.Applicative
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import Control.Monad
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import Control.Monad.Freer
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ifte :: Member NonDetEff r
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=> Eff r a -> (a -> Eff r b) -> Eff r b -> Eff r b
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ifte t th el = msplit t >>= maybe el (\(a,m) -> th a <|> (m >>= th))
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generatePrimes :: Member NonDetEff r => [Int] -> Eff r Int
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generatePrimes xs = do
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n <- gen
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ifte (do d <- gen
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guard $ d < n && n `mod` d == 0)
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(const mzero)
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(return n)
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where gen = msum (fmap return xs)
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testIfte :: [Int] -> [Int]
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testIfte = run . makeChoiceA . generatePrimes
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