Make charCodeAt safe, add unsafe versions of charAt, charCodeAt

README.md

@@ -31,7 +31,7 @@
 
     charAt :: Number -> String -> Maybe Char
 
-    charCodeAt :: Number -> String -> Number
+    charCodeAt :: Number -> String -> Maybe Number
 
     drop :: Number -> String -> String
 
@@ -104,4 +104,13 @@
 
     split :: Regex -> String -> [String]
 
-    test :: Regex -> String -> Boolean
+    test :: Regex -> String -> Boolean
+
+
+## Module Data.String.Unsafe
+
+### Values
+
+    charAt :: Number -> String -> Char
+
+    charCodeAt :: Number -> String -> Number

src/Data/String.purs

@@ -37,12 +37,14 @@ module Data.String
   fromChar :: Char -> String
   fromChar = charString
 
-  foreign import charCodeAt
-    "function charCodeAt(i) {\
-    \  return function(s) {\
-    \    return s.charCodeAt(i); \
-    \  };\
-    \}" :: Number -> String -> Number
+  foreign import _charCodeAt
+    "function _charCodeAt(i, s, Just, Nothing) {\
+    \  if (i < 0 || i >= s.length) return Nothing;\
+    \  else return Just(s.charCodeAt(i));\
+    \}" :: forall a. Fn4 Number String (a -> Maybe a) (Maybe a) (Maybe Number)
+
+  charCodeAt :: Number -> String -> Maybe Number
+  charCodeAt n s = runFn4 _charCodeAt n s Just Nothing
 
   foreign import fromCharArray
     "function fromCharArray(a) {\
@@ -123,7 +125,7 @@ module Data.String
     \  };\
     \}" :: String -> String -> [String]
 
-  foreign import toCharArray 
+  foreign import toCharArray
     "function toCharArray(s) {\
     \   return s.split('');\
     \}" :: String -> [Char]

src/Data/String/Unsafe.purs

@@ -0,0 +1,24 @@
+module Data.String.Unsafe
+  ( charAt
+  , charCodeAt
+  ) where
+
+  import Data.Char
+
+  foreign import charCodeAt
+    """
+    function charCodeAt(i) {
+      return function(s) {
+        return s.charCodeAt(i);
+      };
+    }
+    """ :: Number -> String -> Number
+
+  foreign import charAt
+    """
+    function charAt(i) {
+      return function(s) {
+        return s.charAt(i);
+      };
+    }
+    """ :: Number -> String -> Char