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/Validation.hs | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) create mode 100644 Haskell-book/15/semigroup/src/Validation.hs (limited to 'Haskell-book/15/semigroup/src/Validation.hs') diff --git a/Haskell-book/15/semigroup/src/Validation.hs b/Haskell-book/15/semigroup/src/Validation.hs new file mode 100644 index 0000000..a5d1c9c --- /dev/null +++ b/Haskell-book/15/semigroup/src/Validation.hs @@ -0,0 +1,17 @@ +module Validation where + +import Data.Semigroup +import Test.QuickCheck (arbitrary, Arbitrary(..), frequency) + +data Validation a b = Failure a | Success b deriving (Eq, Show) + +instance Semigroup a => Semigroup (Validation a b) where + (Success x) <> _ = Success x + _ <> (Success x) = Success x + (Failure x) <> (Failure y) = Failure $ x <> y + +instance (Arbitrary a, Arbitrary b) => Arbitrary (Validation a b) where + arbitrary = do + x <- arbitrary + y <- arbitrary + frequency [ (1, return $ Success x), (1, return $ Failure y) ] -- cgit v1.2.3