From e1d9e62b72f301ea2083a25bf32309fdfee34894 Mon Sep 17 00:00:00 2001
From: Yorick Peterse <yorickpeterse@gmail.com>
Date: Mon, 1 Sep 2014 20:48:11 +0200
Subject: [PATCH] Support for the XPath "!=" operator.

---
 lib/oga/xpath/evaluator.rb                    | 12 +++++
 .../oga/xpath/evaluator/operators/neq_spec.rb | 50 +++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 spec/oga/xpath/evaluator/operators/neq_spec.rb

diff --git a/lib/oga/xpath/evaluator.rb b/lib/oga/xpath/evaluator.rb
index 7b43cf7..3416564 100644
--- a/lib/oga/xpath/evaluator.rb
+++ b/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.
       #
diff --git a/spec/oga/xpath/evaluator/operators/neq_spec.rb b/spec/oga/xpath/evaluator/operators/neq_spec.rb
new file mode 100644
index 0000000..9e2d55b
--- /dev/null
+++ b/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