Function array_diff now compared to using the "-" operator on arrays.

array/array_diff.markdown

@@ -1,27 +1,42 @@
 # array_diff
 
-We can find the difference between two arrays using the `Enumerable#reject`
-method. This method rebuilds an array based on conditions that are evaluated
-in a block. In the block we simply reject any element of the array that is in
-the comparison array.
+In Ruby, many operators are implemented as methods, and you can even redefine them.
 
 {{code:php
     $animals1 = array('cat', 'dog', 'bat', 'rat');
-    $animals2 = array('cat', 'dog');
+    $animals2 = array('bat', 'rat');
 
     $result = array_diff($animals1, $animals2);
     var_export($result);
-    // => array(2 => 'bat', 3 => 'rat')
+    // => array(0 => 'cat', 1 => 'dog')
 }}
 
 {{code:ruby
-    animals1 = ['cat', 'dog', 'bat', 'rat']
-    animals2 = ['cat', 'dog']
+    ['cat', 'dog', 'bat', 'rat'] - ['bat', 'rat']
+    # => ["cat", "dog"]
+}}
+
+That is equivalent to calling:
 
-    p animals1.reject {|a| animals2.include?(a) }
-    # => ["bat", "rat"]
+{{code:ruby
+    ['cat', 'dog', 'bat', 'rat'].-(['bat', 'rat'])
+    # => ["cat", "dog"]
 }}
 
+If you don't quite agree with Ruby on how exclusions should be handled, Ruby lets you have it your way:
+
+{{code:ruby
+	def Array
+		def - other
+			self.each_with_index do |item, i|
+				self[i] += '-blacklisted' if other.include? item
+			end
+		end
+	end
+
+    ['cat', 'dog', 'bat', 'rat'] - ['bat', 'rat']
+    # => ["cat", "dog", "bat-blacklisted", "rat-blacklisted"]
+}}
 
 {{related:
     array/array_diff_assoc