Fix bug when comparing node with nil

CHANGELOG.md

@@ -2,6 +2,10 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased][unreleased]
+### Fixed
+- Fix a bug in `Libsvm::Node#==` when comparing with `nil`.
+
 ## [1.3.1] - 2015-03-21
 ### Fixed
 - Spelling and punctuation in documentation comments

lib/libsvm/node.rb

@@ -90,13 +90,15 @@ def initialize(index=0, value=0.0)
       self.value = value
     end
 
-    # Compare features for equality.
+    # Compare feature node for equality.
     #
     # Nodes with equal index and value are equal.
     #
     # @return [Boolean]
-    def ==(other)
-      index == other.index && value == other.value
+    def == (other)
+      other.class == self.class &&
+        index == other.index &&
+        value == other.value
     end
 
     def inspect

spec/node_spec.rb

@@ -67,6 +67,10 @@
     expect(ary.map(&:index)).to eq([3, 5, 6, 10])
   end
 
+  it "compares with nil" do
+    expect(Node.new(1,2)).to_not eq(nil)
+  end
+
   it "implements value equality" do
     expect(Node[1, 0.1]).to eq(Node[1, 0.1])
   end