Merge pull request #25 from hdgarrood/semigroup-map

Add semigroup and monoid instances

Author: paf31

README.md

@@ -15,6 +15,10 @@
 
     instance functorMap :: P.Functor (Map k)
 
+    instance monoidMap :: (P.Ord k) => Monoid (Map k v)
+
+    instance semigroupMap :: (P.Ord k) => P.Semigroup (Map k v)
+
     instance showMap :: (P.Show k, P.Show v) => P.Show (Map k v)
 
     instance traversableMap :: (P.Ord k) => Traversable (Map k)

src/Data/Map.purs

@@ -32,6 +32,7 @@ import qualified Prelude as P
 import qualified Data.Array as A
 import Data.Maybe
 import Data.Tuple
+import Data.Monoid (Monoid)
 import Data.Foldable (foldl, foldMap, foldr, Foldable)
 import Data.Traversable (traverse, Traversable)
 
@@ -47,6 +48,12 @@ instance eqMap :: (P.Eq k, P.Eq v) => P.Eq (Map k v) where
 instance showMap :: (P.Show k, P.Show v) => P.Show (Map k v) where
   show m = "fromList " P.++ P.show (toList m)
 
+instance semigroupMap :: (P.Ord k) => P.Semigroup (Map k v) where
+  (<>) = union
+
+instance monoidMap :: (P.Ord k) => Monoid (Map k v) where
+  mempty = empty
+
 instance functorMap :: P.Functor (Map k) where
   (<$>) _ Leaf = Leaf
   (<$>) f (Two left k v right) = Two (f P.<$> left) k (f v) (f P.<$> right)