Merge pull request #1 from purescript/mapmaybe

Add mapMaybe

Author: paf31

README.md

@@ -53,6 +53,8 @@
 
     map :: forall a b. (a -> b) -> [a] -> [b]
 
+    mapMaybe :: forall a b. (a -> Maybe b) -> [a] -> [b]
+
     nub :: forall a. (Eq a) => [a] -> [a]
 
     nubBy :: forall a. (a -> a -> Prim.Boolean) -> [a] -> [a]

src/Data/Array.purs

@@ -8,6 +8,7 @@ module Data.Array
   , init
   , null
   , map
+  , mapMaybe
   , length
   , elem
   , elemIndex
@@ -79,7 +80,7 @@ foreign import length
   "function length (xs) {\
   \  return xs.length;\
   \}" :: forall a. [a] -> Number
-  
+
 foreign import elem
   "function elem(e) {\
   \  return function (l) {\
@@ -100,7 +101,7 @@ foreign import elemLastIndex
   \    return l.lastIndexOf(e);\
   \  };\
   \}" :: forall a. a -> [a] -> Number
-  
+
 foreign import append
   "function append (l1) {\
   \  return function (l2) {\
@@ -186,7 +187,7 @@ foreign import concatMap
   \    return result;\
   \  };\
   \}" :: forall a b. (a -> [b]) -> [a] -> [b]
-  
+
 foreign import map
   "function map (f) {\
   \  return function (arr) {\
@@ -199,6 +200,9 @@ foreign import map
   \  };\
   \}" :: forall a b. (a -> b) -> [a] -> [b]
 
+mapMaybe :: forall a b. (a -> Maybe b) -> [a] -> [b]
+mapMaybe f = concatMap (maybe [] singleton <<< f)
+
 foreign import filter
   "function filter (f) {\
   \  return function (arr) {\