reverted _.buildLookup, restoring _.without to it's previous implemen…

…tation, adding a test for object identity

test/arrays.js

@@ -46,6 +46,10 @@ $(document).ready(function() {
     equals(_.without(list, 0, 1).join(', '), '2, 3, 4', 'can remove all instances of an object');
     var result = (function(){ return _.without(arguments, 0, 1); })(1, 2, 1, 0, 3, 1, 4);
     equals(result.join(', '), '2, 3, 4', 'works on an arguments object');
+
+    var list = [{one : 1}, {two : 2}];
+    ok(_.without(list, {one : 1}).length == 2, 'uses real object identity for comparisons.');
+    ok(_.without(list, list[0]).length == 1, 'ditto.');
   });
 
   test("arrays: uniq", function() {

test/collections.js

@@ -164,12 +164,5 @@ $(document).ready(function() {
   test('collections: size', function() {
     equals(_.size({one : 1, two : 2, three : 3}), 3, 'can compute the size of an object');
   });
-
-  test('collections: buildLookup', function() {
-    same(_.buildLookup([1,'hi']), {1:true, 'hi':true}, 'defaults values to true');
-    same(_.buildLookup([1,'hi'], 1), {1:1, 'hi':1}, 'can override value');
-    same(_.buildLookup({5:'five'}), {five: true}, 'making a map from an object uses its values');
-  });
-
 
 });

test/objects.js

@@ -11,7 +11,7 @@ $(document).ready(function() {
   });
 
   test("objects: functions", function() {
-    var expected = ["all", "any", "bind", "bindAll", "breakLoop", "buildLookup", "clone", "compact",
+    var expected = ["all", "any", "bind", "bindAll", "breakLoop", "clone", "compact",
     "compose","defer", "delay", "detect", "each", "every", "extend", "filter", "first",
     "flatten", "foldl", "foldr", "forEach", "functions", "head", "identity", "include",
     "indexOf", "inject", "intersect", "invoke", "isArguments", "isArray", "isDate", "isElement", "isEmpty", "isEqual",

underscore.js

@@ -252,24 +252,6 @@
     return _.toArray(obj).length;
   };
 
-  // Build a lookup map from a collection.
-  // Pay a little memory upfront to make searching a collection for a
-  // value faster later
-  // e.g:
-  //
-  //  var lookup = _.buildLookup([1,2,8])  // {1: true, 2: true, 8: true}
-  //  lookup[key]   // instead of: _.include(array, key)
-  //
-  // See example usage in #without
-  // By default sets the value to true, can pass in a value to use instead
-  _.buildLookup = function (obj, useValue) {
-    useValue = (useValue === undefined)?  true :  useValue;
-    return _.reduce(obj, {}, function (memo, value) {
-      memo[value] = useValue;
-      return memo;
-    });
-  };
-
   // -------------------------- Array Functions: ------------------------------
 
   // Get the first element of an array. Passing "n" will return the first N
@@ -308,8 +290,8 @@
 
   // Return a version of the array that does not contain the specified value(s).
   _.without = function(array) {
-    var lookup = _.buildLookup(_.rest(arguments));
-    return _.filter(array, function(value){ return !lookup[value]; });
+    var values = _.rest(arguments);
+    return _.select(array, function(value){ return !_.include(values, value); });
   };
 
   // Produce a duplicate-free version of the array. If the array has already