Support for the XPath round() function.

lib/oga/xpath/evaluator.rb

@@ -1216,6 +1216,22 @@ module Oga
         return number.nan? ? number : number.ceil.to_f
       end
 
+      ##
+      # Processes the `round()` function call.
+      #
+      # This function call rounds the 1st argument to the closest integer number
+      # and then returns that number as a float.
+      #
+      # @param [Oga::XML::NodeSet] context
+      # @param [Oga::XPath::Node] expression
+      # @return [Float]
+      #
+      def on_call_round(context, expression)
+        number = on_call_number(context, expression)
+
+        return number.nan? ? number : number.round.to_f
+      end
+
       ##
       # Processes an `(int)` node.
       #

spec/oga/xpath/evaluator/calls/round_spec.rb

@@ -0,0 +1,30 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'round() function' do
+    before do
+      @document  = parse('<root>10.123</root>')
+      @evaluator = described_class.new(@document)
+    end
+
+    example 'return the rounded value of a literal number' do
+      @evaluator.evaluate('round(10.123)').should == 10.0
+    end
+
+    example 'return the rounded value of a literal string' do
+      @evaluator.evaluate('round("10.123")').should == 10.0
+    end
+
+    example 'return the rounded value of a node set' do
+      @evaluator.evaluate('round(root)').should == 10.0
+    end
+
+    example 'return NaN for empty node sets' do
+      @evaluator.evaluate('round(foo)').should be_nan
+    end
+
+    example 'return NaN for an empty literal string' do
+      @evaluator.evaluate('round("")').should be_nan
+    end
+  end
+end