From 98329e0a3dd4f78b5d815ac3896272ec70904901 Mon Sep 17 00:00:00 2001 From: Eugen Wissner Date: Thu, 11 Dec 2025 10:28:11 +0100 Subject: Add remaining haskell book exercises --- Haskell-book/18/Instance/src/Identity.hs | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 Haskell-book/18/Instance/src/Identity.hs (limited to 'Haskell-book/18/Instance/src/Identity.hs') diff --git a/Haskell-book/18/Instance/src/Identity.hs b/Haskell-book/18/Instance/src/Identity.hs new file mode 100644 index 0000000..13cd1b2 --- /dev/null +++ b/Haskell-book/18/Instance/src/Identity.hs @@ -0,0 +1,24 @@ +module Identity where + +import Test.QuickCheck +import Test.QuickCheck.Checkers + +newtype Identity a = Identity a + deriving (Eq, Ord, Show) + +instance Functor Identity where + fmap f (Identity x) = Identity $ f x + +instance Applicative Identity where + pure = Identity + (Identity f) <*> x = fmap f x + +instance Monad Identity where + return = pure + (Identity x) >>= f = f x + +instance Arbitrary a => Arbitrary (Identity a) where + arbitrary = fmap Identity $ arbitrary + +instance Eq a => EqProp (Identity a) where + (=-=) = eq -- cgit v1.2.3