Fixes jashkenas#1503. Stops the bikeshedding.

index.html

@@ -262,7 +262,7 @@
       <li>- <a href="#once">once</a></li>
       <li>- <a href="#after">after</a></li>
       <li>- <a href="#wrap">wrap</a></li>
-      <li>- <a href="#complement">complement</a></li>
+      <li>- <a href="#negate">negate</a></li>
       <li>- <a href="#compose">compose</a></li>
     </ul>
 
@@ -1223,14 +1223,13 @@ <h2 id="functions">Function (uh, ahem) Functions</h2>
 =&gt; 'before, hello: moe, after'
 </pre>
 
-      <p id="complement">
-        <b class="header">complement</b><code>_.complement(predicate)</code>
+      <p id="negate">
+        <b class="header">negate</b><code>_.negate(predicate)</code>
         <br />
-        Returns a function that takes the same arguments as <b>predicate</b>,
-        has the same effects, if any, and returns the opposite truth value.
+        Returns a new negated version of the <b>predicate</b> function.
       </p>
       <pre>
-var isFalsy = _.complement(Boolean);
+var isFalsy = _.negate(Boolean);
 _.find([-2, -1, 0, 1, 2], isFalsy);
 =&gt; 0
 </pre>

test/functions.js

@@ -388,10 +388,10 @@
     deepEqual(ret, [noop, ['whats', 'your'], 'vector', 'victor']);
   });
 
-  test('complement', function() {
+  test('negate', function() {
     var isOdd = function(n){ return (n & 1) == 1; };
-    equal(_.complement(isOdd)(2), true, 'should return the complement of the given function');
-    equal(_.complement(isOdd)(3), false, 'should return the complement of the given function');
+    equal(_.negate(isOdd)(2), true, 'should return the complement of the given function');
+    equal(_.negate(isOdd)(3), false, 'should return the complement of the given function');
   });
 
   test('compose', function() {

underscore.js

@@ -179,7 +179,7 @@
 
   // Return all the elements for which a truth test fails.
   _.reject = function(obj, predicate, context) {
-    return _.filter(obj, _.complement(predicate), context);
+    return _.filter(obj, _.negate(predicate), context);
   };
 
   // Determine whether all of the elements match a truth test.
@@ -782,9 +782,8 @@
     return _.partial(wrapper, func);
   };
 
-  // Returns a function that takes the same arguments as the given predicate,
-  // has the same effects, if any, and returns the opposite truth value.
-  _.complement = function(predicate) {
+  // Returns a negated version of the passed-in predicate.
+  _.negate = function(predicate) {
     return function() {
       return !predicate.apply(this, arguments);
     };