Add append and concat functions, organize docs better

libraries/Native/String.js

@@ -22,6 +22,12 @@ Elm.Native.String.make = function(elm) {
         return (hd = str[0]) ? Maybe.Just(Utils.Tuple2(Utils.chr(hd), str.slice(1)))
                               : Maybe.Nothing;
     }
+    function append(a,b) {
+        return a + b;
+    }
+    function concat(strs) {
+        return JS.fromList(strs).join('');
+    }
     function length(str) {
         return str.length;
     }
@@ -191,6 +197,8 @@ Elm.Native.String.make = function(elm) {
         isEmpty: isEmpty,
         cons: F2(cons),
         uncons: uncons,
+        append: F2(append),
+        concat: concat,
         length: length,
         map: F2(map),
         filter: F2(filter),

libraries/String.elm

@@ -3,11 +3,10 @@ module String where
 are enclosed in `"double quotes"`. Strings are *not* lists of characters.
 
 # Basics
-@docs isEmpty, length, cons, uncons, reverse,
-      map, filter, foldl, foldr, any, all, repeat
+@docs isEmpty, length, reverse, repeat
 
-# Split and Join
-@docs split, join, words, lines
+# Building and Splitting
+@docs  cons, uncons, append, concat, split, join, words, lines
 
 # Get Substrings
 @docs sub, left, right, dropLeft, dropRight
@@ -24,6 +23,9 @@ Cosmetic operations such as padding with extra characters or trimming whitespace
 @docs toUpper, toLower,
       pad, padLeft, padRight,
       trim, trimLeft, trimRight
+
+# Higher-Order Functions
+@docs map, filter, foldl, foldr, any, all
 -}
 
 import Native.String
@@ -46,6 +48,21 @@ pattern match on strings exactly as you would with lists.
 uncons : String -> Maybe (Char, String)
 uncons = Native.String.uncons
 
+{-| Append two strings. You can also use [the `(++)` operator](/library/List.elm#++)
+to do this.
+
+      append "butter" "fly" == "butterfly"
+-}
+append : String -> String -> String
+append = Native.String.append
+
+{-| Concatenate many strings into one.
+
+      concat ["never","the","less"] == "nevertheless"
+-}
+concat : [String] -> String
+concat = Native.String.concat
+
 {-| Get the length of a string `(length "innumerable" == 11)` -}
 length : String -> Int
 length = Native.String.length