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58 lines
2.0 KiB
Haskell
58 lines
2.0 KiB
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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import Polysemy.Trace
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import Polysemy.Reader
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runAlt :: Alternative f => Sem '[NonDet] a -> f a
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runAlt = run . runNonDet
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failtrace :: (Member NonDet r, Member Trace r)
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=> Sem r ()
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failtrace = pure () <|> trace "trace"
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failtrace' :: (Member NonDet r, Member Trace r)
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=> Sem r ()
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failtrace' = trace "sim" *> empty <|> trace "salabim"
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inHigherOrder :: Members '[NonDet, Trace, Reader ()] r
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=> Sem r ()
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inHigherOrder = do
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local (\_ -> ()) $ trace "1" <|> trace "2"
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trace "3"
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spec :: Spec
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spec = parallel $ 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 "runNonDetMaybe" $ do
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it "should skip second branch if the first branch succeeds" $ do
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(run . runNonDetMaybe . runTraceList) failtrace
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`shouldBe` Just ([], ())
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(run . runTraceList . runNonDetMaybe) failtrace
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`shouldBe` ([], Just ())
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it "should respect local/global state semantics" $ do
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(run . runNonDetMaybe . runTraceList) failtrace'
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`shouldBe` Just (["salabim"], ())
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(run . runTraceList . runNonDetMaybe) failtrace'
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`shouldBe` (["sim", "salabim"], Just ())
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describe "runNonDet" $ do
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it "should have terrible semantics when <|> is used within\
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\ a higher-order action of a later effect (See Issue #246.)" $ do
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(fst . run . runTraceList . runReader () . runNonDet @[]) inHigherOrder
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`shouldBe` ["1","2","3","3"]
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(fst . run . runTraceList . runReader () . runNonDet @[]) inHigherOrder
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`shouldNotBe` ["1","3","2","3"] -- This is what we actually WANT it to be.
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(fst . run . runTraceList . runNonDet @[] . runReader ()) inHigherOrder
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`shouldBe` ["1","3","2","3"]
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