Merge pull request #43 from jbrownson/master

fix peek to return Maybe, update docs

Author: paf31

docs/Data/Map.md

@@ -175,7 +175,7 @@ of duplicate keys
 #### `unions`
 
 ``` purescript
-unions :: forall k v. (Ord k) => List (Map k v) -> Map k v
+unions :: forall k v f. (Ord k, Foldable f) => f (Map k v) -> Map k v
 ```
 
 Compute the union of a collection of maps

docs/Data/StrMap/ST.md

@@ -27,7 +27,7 @@ Create a new, empty mutable map
 #### `peek`
 
 ``` purescript
-peek :: forall a h r. STStrMap h a -> String -> Eff (st :: ST h | r) a
+peek :: forall a h r. STStrMap h a -> String -> Eff (st :: ST h | r) (Maybe a)
 ```
 
 Get the value for a key in a mutable map

src/Data/StrMap/ST.js

@@ -7,10 +7,14 @@ exports["new"] = function () {
   return {};
 };
 
-exports.peek = function (m) {
-  return function (k) {
-    return function () {
-      return m[k];
+exports.peekImpl = function (just) {
+  return function (nothing) {
+    return function (m) {
+      return function (k) {
+        return function () {
+          return {}.hasOwnProperty.call(m, k) ? just(m[k]) : nothing;
+        };
+      };
     };
   };
 };

src/Data/StrMap/ST.purs

@@ -14,6 +14,7 @@ import Prelude
 
 import Control.Monad.Eff (Eff())
 import Control.Monad.ST (ST())
+import Data.Maybe (Maybe(..))
 
 -- | A reference to a mutable map
 -- |
@@ -26,7 +27,10 @@ foreign import data STStrMap :: * -> * -> *
 foreign import new :: forall a h r. Eff (st :: ST h | r) (STStrMap h a)
 
 -- | Get the value for a key in a mutable map
-foreign import peek :: forall a h r. STStrMap h a -> String -> Eff (st :: ST h | r) a
+peek :: forall a h r. STStrMap h a -> String -> Eff (st :: ST h | r) (Maybe a)
+peek = peekImpl Just Nothing
+
+foreign import peekImpl :: forall a b h r. (a -> b) -> b -> STStrMap h a -> String -> Eff (st :: ST h | r) b
 
 -- | Update the value for a key in a mutable map
 foreign import poke :: forall a h r. STStrMap h a -> String -> a -> Eff (st :: ST h | r) (STStrMap h a)