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/optional/src/Optional.hs | 12 ++++++++++++ 1 file changed, 12 insertions(+) create mode 100644 Haskell-book/15/optional/src/Optional.hs (limited to 'Haskell-book/15/optional/src') diff --git a/Haskell-book/15/optional/src/Optional.hs b/Haskell-book/15/optional/src/Optional.hs new file mode 100644 index 0000000..d85d8a5 --- /dev/null +++ b/Haskell-book/15/optional/src/Optional.hs @@ -0,0 +1,12 @@ +module Optional where + +data Optional a = + Nada + | Only a + deriving (Eq, Show) + +instance Monoid a => Monoid (Optional a) where + mempty = Nada + mappend x Nada = x + mappend Nada x = x + mappend (Only x) (Only y) = Only (mappend x y) -- cgit v1.2.3