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/15/semigroup/src/Comp.hs | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 Haskell-book/15/semigroup/src/Comp.hs (limited to 'Haskell-book/15/semigroup/src/Comp.hs') diff --git a/Haskell-book/15/semigroup/src/Comp.hs b/Haskell-book/15/semigroup/src/Comp.hs new file mode 100644 index 0000000..f7224da --- /dev/null +++ b/Haskell-book/15/semigroup/src/Comp.hs @@ -0,0 +1,22 @@ +module Comp where + +import Data.Semigroup +import Test.QuickCheck + +newtype Comp a = + Comp { unComp :: (a -> a) } + +instance Semigroup a => Semigroup (Comp a) where + (Comp f1) <> (Comp f2) = Comp f + where f x = (f1 x) <> (f2 x) + +instance Monoid a => Monoid (Comp a) where + mempty = Comp $ \_ -> mempty + mappend (Comp f1) (Comp f2) = Comp f + where f x = mappend (f1 x) (f2 x) + +instance (Arbitrary a, CoArbitrary a) => Arbitrary (Comp a) where + arbitrary = fmap Comp arbitrary + +instance Show (Comp a) where + show _ = "a -> a" -- cgit v1.2.3