add tests + docs

Author: hdgarrood

README.md

@@ -48,6 +48,8 @@
 
     singleton :: forall k v. k -> v -> Map k v
 
+    size :: forall k v. Map k v -> Number
+
     toList :: forall k v. Map k v -> [Tuple k v]
 
     union :: forall k v. (P.Ord k) => Map k v -> Map k v -> Map k v

src/Data/Map.purs

@@ -23,7 +23,8 @@ module Data.Map
     values,
     union,
     unions,
-    map
+    map,
+    size
   ) where
 
 import qualified Prelude as P

tests/Data/Map.purs

@@ -4,7 +4,7 @@ import Debug.Trace
 
 import Data.Maybe
 import Data.Tuple
-import Data.Array (map)
+import Data.Array (map, length, nubBy)
 import Data.Function (on)
 import Data.Foldable (foldl)
 
@@ -165,3 +165,8 @@ mapTests = do
 
   trace "Union is idempotent"
   quickCheck $ \m1 m2 -> (m1 `M.union` m2) == ((m1 `M.union` m2) `M.union` (m2 :: M.Map SmallKey Number))
+
+  trace "size"
+  quickCheck $ \xs ->
+    let xs' = nubBy ((==) `on` fst) xs
+    in  M.size (M.fromList xs') == length (xs' :: [Tuple SmallKey Number])