Support for the XPath "!=" operator.

lib/oga/xpath/evaluator.rb

@@ -742,6 +742,18 @@ module Oga
         return left == right
       end
 
+      ##
+      # Processes the `!=` operator.
+      #
+      # This operator does the exact opposite of the `=` operator. See {#on_eq}
+      # for more information.
+      #
+      # @see [#on_eq]
+      #
+      def on_neq(ast_node, context)
+        return !on_eq(ast_node, context)
+      end
+
       ##
       # Delegates function calls to specific handlers.
       #

spec/oga/xpath/evaluator/operators/neq_spec.rb

@@ -0,0 +1,50 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'not-equal operator' do
+    before do
+      @document  = parse('<root><a>10</a><b>10</b></root>')
+      @evaluator = described_class.new(@document)
+    end
+
+    example 'return true if two numbers are not equal' do
+      @evaluator.evaluate('10 != 20').should == true
+    end
+
+    example 'return false if two numbers are equal' do
+      @evaluator.evaluate('10 != 10').should == false
+    end
+
+    example 'return true if a number and a string are not equal' do
+      @evaluator.evaluate('10 != "20"').should == true
+    end
+
+    example 'return true if two strings are not equal' do
+      @evaluator.evaluate('"10" != "20"').should == true
+    end
+
+    example 'return true if a string and a number are not equal' do
+      @evaluator.evaluate('"10" != 20').should == true
+    end
+
+    example 'return false if two strings are equal' do
+      @evaluator.evaluate('"a" != "a"').should == false
+    end
+
+    example 'return true if two node sets are not equal' do
+      @evaluator.evaluate('root != root/b').should == true
+    end
+
+    example 'return false if two node sets are equal' do
+      @evaluator.evaluate('root/a != root/b').should == false
+    end
+
+    example 'return true if a node set and a number are not equal' do
+      @evaluator.evaluate('root/a != 20').should == true
+    end
+
+    example 'return true if a node set and a string are not equal' do
+      @evaluator.evaluate('root/a != "20"').should == true
+    end
+  end
+end