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35 lines
944 B
Haskell
35 lines
944 B
Haskell
module AlternativeSpec where
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import Polysemy
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import Polysemy.NonDet
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import Test.Hspec
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import Control.Applicative
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semFail :: Member NonDet r => Maybe Bool -> Sem r Bool
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semFail mb = do
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Just b <- pure mb
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pure b
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runAlt :: Alternative f => Sem '[NonDet] a -> f a
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runAlt = run . runNonDet
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spec :: Spec
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spec = do
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describe "Alternative instance" $ do
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it "should choose the first branch" $ do
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runAlt (pure '1' <|> pure '2') `shouldBe` (Just '1')
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it "should failover" $ do
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runAlt (empty <|> pure '2') `shouldBe` (Just '2')
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runAlt (pure '1' <|> empty) `shouldBe` (Just '1')
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describe "MonadFail instance" $ do
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it "should call empty via fail" $ do
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runAlt (semFail Nothing) `shouldBe` Nothing
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runAlt (semFail Nothing) `shouldBe` []
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it "should work fine for non-failing patterns" $ do
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runAlt (semFail $ Just True) `shouldBe` Just True
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runAlt (semFail $ Just False) `shouldBe` [False]
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