Support for the XPath "and" operator.

lib/oga/xpath/evaluator.rb

@@ -592,6 +592,23 @@ module Oga
         return process(left, context) + process(right, context)
       end
 
+      ##
+      # Processes the `and` operator.
+      #
+      # This operator returns true if both the left and right expression
+      # evaluate to `true`. If the first expression evaluates to `false` the
+      # right expression is ignored.
+      #
+      # @param [Oga::XPath::Node] ast_node
+      # @param [Oga::XML::NodeSet] context
+      # @return [TrueClass|FalseClass]
+      #
+      def on_and(ast_node, context)
+        left, right = *ast_node
+
+        return on_call_boolean(context, left) && on_call_boolean(context, right)
+      end
+
       ##
       # Delegates function calls to specific handlers.
       #

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

@@ -0,0 +1,32 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'and operator' do
+    before do
+      @document  = parse('<root><a>1</a><b>1</b></root>')
+      @evaluator = described_class.new(@document)
+    end
+
+    example 'return true if both boolean literals are true' do
+      @evaluator.evaluate('true() and true()').should == true
+    end
+
+    example 'return false if one of the boolean literals is false' do
+      @evaluator.evaluate('true() and false()').should == false
+    end
+
+    example 'return true if both node sets are non empty' do
+      @evaluator.evaluate('root/a and root/b').should == true
+    end
+
+    example 'false false if one of the node sets is empty' do
+      @evaluator.evaluate('root/a and root/c').should == false
+    end
+
+    example 'skip the right expression if the left one evaluates to false' do
+      @evaluator.should_not receive(:on_call_true)
+
+      @evaluator.evaluate('false() and true()').should == false
+    end
+  end
+end