Merging in jashkenas#194, adding an iterator to _.uniq

index.html

@@ -592,12 +592,14 @@ <h2>Array Functions</h2>
 </pre>
 
       <p id="uniq">
-        <b class="header">uniq</b><code>_.uniq(array, [isSorted])</code>
+        <b class="header">uniq</b><code>_.uniq(array, [isSorted], [iterator])</code>
         <span class="alias">Alias: <b>unique</b></span>
         <br />
         Produces a duplicate-free version of the <b>array</b>, using <i>===</i> to test
         object equality. If you know in advance that the <b>array</b> is sorted,
         passing <i>true</i> for <b>isSorted</b> will run a much faster algorithm.
+        If you want to compute unique items based on a transformation, pass an
+        <b>iterator</b> function.
       </p>
       <pre>
 _.uniq([1, 2, 1, 3, 1, 4]);

test/arrays.js

@@ -61,6 +61,14 @@ $(document).ready(function() {
     var list = [1, 1, 1, 2, 2, 3];
     equals(_.uniq(list, true).join(', '), '1, 2, 3', 'can find the unique values of a sorted array faster');
 
+    var list = [{name:'moe'}, {name:'curly'}, {name:'larry'}, {name:'curly'}];
+    var iterator = function(value) { return value.name; };
+    equals(_.map(_.uniq(list, false, iterator), iterator).join(', '), 'moe, curly, larry', 'can find the unique values of an array using a custom iterator');
+
+    var iterator = function(value) { return value +1; };
+    var list = [1, 2, 2, 3, 4, 4];
+    equals(_.uniq(list, true, iterator).join(', '), '1, 2, 3, 4', 'iterator works with sorted array');
+
     var result = (function(){ return _.uniq(arguments); })(1, 2, 1, 3, 1, 4);
     equals(result.join(', '), '1, 2, 3, 4', 'works on an arguments object');
   });

underscore.js

@@ -333,11 +333,17 @@
   // Produce a duplicate-free version of the array. If the array has already
   // been sorted, you have the option of using a faster algorithm.
   // Aliased as `unique`.
-  _.uniq = _.unique = function(array, isSorted) {
-    return _.reduce(array, function(memo, el, i) {
-      if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) memo[memo.length] = el;
+  _.uniq = _.unique = function(array, isSorted, iterator) {
+    var initial = iterator ? _.map(array, iterator) : array;
+    var result = [];
+    _.reduce(initial, function(memo, el, i) {
+      if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) {
+        memo[memo.length] = el;
+        result[result.length] = array[i];
+      }
       return memo;
     }, []);
+    return result;
   };
 
   // Produce an array that contains the union: each distinct element from all of