add slice

Author: themattchan

src/Data/String.js

@@ -131,6 +131,14 @@ exports.drop = function (n) {
   };
 };
 
+exports.slice = function (b) {
+  return function (e) {
+    return function (s) {
+      return s.slice(b, e);
+    };
+  };
+};
+
 exports.count = function (p) {
   return function (s) {
     var i = 0;

src/Data/String.purs

@@ -26,6 +26,7 @@ module Data.String
   , drop
   , dropRight
   , dropWhile
+  , slice
   , stripPrefix
   , stripSuffix
   , count
@@ -172,6 +173,17 @@ takeWhile p s = take (count p s) s
 dropWhile :: (Char -> Boolean) -> String -> String
 dropWhile p s = drop (count p s) s
 
+-- | Returns the substring at indices [begin, end).
+-- | If either index is negative, it is normalized to `length s - index`,
+-- | where `s` is the input string. An empty string is returned if either
+-- | index is out of bounds or if `begin > end`.
+-- |
+-- | ```purescript
+-- | slice 0 1 "purescript" == "p"
+-- | slice 3 6 "purescript" == "ecr"
+-- | slice -4 -1 "purescript" == "rip"
+foreign import slice :: Int -> Int -> String -> String
+
 -- | If the string starts with the given prefix, return the portion of the
 -- | string left after removing it, as a Just value. Otherwise, return Nothing.
 -- |