Added a null,singleton,uncons,takeWhile and dropWhile to Data.String

README.md

@@ -33,8 +33,12 @@
 
     charCodeAt :: Number -> String -> Maybe Number
 
+    count :: (Char -> Boolean) -> String -> Number
+
     drop :: Number -> String -> String
 
+    dropWhile :: (Char -> Boolean) -> String -> String
+
     fromChar :: Char -> String
 
     fromCharArray :: [Char] -> String
@@ -53,12 +57,18 @@
 
     localeCompare :: String -> String -> Number
 
+    null :: String -> Boolean
+
     replace :: String -> String -> String -> String
 
+    singleton :: Char -> String
+
     split :: String -> String -> [String]
 
     take :: Number -> String -> String
 
+    takeWhile :: (Char -> Boolean) -> String -> String
+
     toCharArray :: String -> [Char]
 
     toLower :: String -> String
@@ -67,14 +77,16 @@
 
     trim :: String -> String
 
+    uncons :: String -> Maybe { tail :: String, head :: Char }
+
 
 ## Module Data.String.Regex
 
 ### Types
 
     data Regex :: *
 
-    type RegexFlags  = { unicode :: Boolean, sticky :: Boolean, multiline :: Boolean, ignoreCase :: Boolean, global :: Boolean }
+    type RegexFlags = { unicode :: Boolean, sticky :: Boolean, multiline :: Boolean, ignoreCase :: Boolean, global :: Boolean }
 
 
 ### Type Class Instances

src/Data/String.purs

@@ -8,11 +8,17 @@ module Data.String
     indexOf',
     lastIndexOf,
     lastIndexOf',
+    null,
+    uncons,
     length,
+    singleton,
     localeCompare,
     replace,
+    count,
     take,
+    takeWhile,
     drop,
+    dropWhile,
     split,
     toCharArray,
     toLower,
@@ -24,6 +30,7 @@ module Data.String
   import Data.Maybe
   import Data.Char
   import Data.Function
+  import qualified Data.String.Unsafe as U
 
   foreign import _charAt
     """
@@ -38,6 +45,9 @@ module Data.String
   fromChar :: Char -> String
   fromChar = charString
 
+  singleton :: Char -> String
+  singleton = fromChar
+
   foreign import _charCodeAt
     """
     function _charCodeAt(i, s, Just, Nothing) {
@@ -48,6 +58,19 @@ module Data.String
   charCodeAt :: Number -> String -> Maybe Number
   charCodeAt n s = runFn4 _charCodeAt n s Just Nothing
 
+  null :: String -> Boolean
+  null s = length s == 0
+
+  uncons :: String -> Maybe {head :: Char, tail :: String}
+  uncons s | null s = Nothing
+  uncons s = Just {head : U.charAt 0 s, tail : drop 1 s}
+
+  takeWhile :: (Char -> Boolean) -> String -> String
+  takeWhile p s = take (count p s) s
+
+  dropWhile :: (Char -> Boolean) -> String -> String
+  dropWhile p s = drop (count p s) s
+
   foreign import fromCharArray
     """
     function fromCharArray(a) {
@@ -140,6 +163,17 @@ module Data.String
     }
     """ :: Number -> String -> String
 
+  foreign import count
+    """
+    function count(p){      
+      return function(s){
+        var i;
+        for(i = 0; i < s.length && p(s.charAt(i)); i++){};
+        return i;
+      };      
+    }
+    """ :: (Char -> Boolean) -> String -> Number
+
   foreign import split
     """
     function split(sep) {