Haskell-book/15/semigroup/src/Bool.hs


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module Bool where

import Data.Semigroup
import Test.QuickCheck

newtype BoolConj = BoolConj Bool deriving (Eq, Show)

instance Semigroup BoolConj where
    (BoolConj True) <> (BoolConj True) = BoolConj True
    _ <> _ = BoolConj False

instance Monoid BoolConj where
    mempty = BoolConj True
    mappend = (<>)

instance Arbitrary BoolConj where
    arbitrary = fmap BoolConj arbitrary

newtype BoolDisj = BoolDisj Bool deriving (Eq, Show)

instance Semigroup BoolDisj where
    (BoolDisj False) <> (BoolDisj False) = BoolDisj False
    _ <> _ = BoolDisj True

instance Monoid BoolDisj where
    mempty = BoolDisj False
    mappend = (<>)

instance Arbitrary BoolDisj where
    arbitrary = fmap BoolDisj arbitrary