1 files changed, 19 insertions, 0 deletions
diff --git a/Haskell-book/12/Maybe.hs b/Haskell-book/12/Maybe.hs
new file mode 100644
index 0000000..e83176e
--- /dev/null
+++ b/Haskell-book/12/Maybe.hs
@@ -0,0 +1,19 @@
+module Maybe where
+
+--
+-- 1
+--
+isJust :: Maybe a -> Bool
+isJust (Just _) = True
+isJust Nothing = False
+
+isNothing :: Maybe a -> Bool
+isNothing (Just _) = False
+isNothing Nothing = True
+
+--
+-- 2
+--
+mayybee :: b -> (a -> b) -> Maybe a -> b
+mayybee v f Nothing   = b
+mayybee v f (Maybe x) = f x