mirror of
https://github.com/polysemy-research/polysemy.git
synced 2024-12-12 13:06:18 +03:00
35 lines
944 B
Haskell
35 lines
944 B
Haskell
|
module AlternativeSpec where
|
||
|
|
|
||
|
|
import Polysemy
|
||
|
|
import Polysemy.NonDet
|
||
|
|
import Test.Hspec
|
||
|
|
import Control.Applicative
|
||
|
|
|
||
|
|
semFail :: Member NonDet r => Maybe Bool -> Sem r Bool
|
||
|
|
semFail mb = do
|
||
|
|
Just b <- pure mb
|
||
|
|
pure b
|
||
|
|
|
||
|
|
|
||
|
|
runAlt :: Alternative f => Sem '[NonDet] a -> f a
|
||
|
|
runAlt = run . runNonDet
|
||
|
|
|
||
|
|
|
||
|
|
spec :: Spec
|
||
|
|
spec = do
|
||
|
|
describe "Alternative instance" $ do
|
||
|
|
it "should choose the first branch" $ do
|
||
|
|
runAlt (pure '1' <|> pure '2') `shouldBe` (Just '1')
|
||
|
|
it "should failover" $ do
|
||
|
|
runAlt (empty <|> pure '2') `shouldBe` (Just '2')
|
||
|
|
runAlt (pure '1' <|> empty) `shouldBe` (Just '1')
|
||
|
|
|
||
|
|
describe "MonadFail instance" $ do
|
||
|
|
it "should call empty via fail" $ do
|
||
|
|
runAlt (semFail Nothing) `shouldBe` Nothing
|
||
|
|
runAlt (semFail Nothing) `shouldBe` []
|
||
|
|
it "should work fine for non-failing patterns" $ do
|
||
|
|
runAlt (semFail $ Just True) `shouldBe` Just True
|
||
|
|
runAlt (semFail $ Just False) `shouldBe` [False]
|
||
|
|
|