Changes for performance as well as some general refactoring

lib/core_extensions/array.rb

@@ -1,29 +1,19 @@
 class Array
-  def classification
-    collect(&:last)
-  end
-
-  # calculate information entropy
   def entropy
-    return 0 if empty?
-
-    info = {}
-    each do |i|
-      info[i] = !info[i] ? 1 : (info[i] + 1)
+    each_with_object(Hash.new(0)) do |i, result|
+      result[i] += 1
+    end.values.inject(0) do |sum, count|
+      percentage = count.to_f / length
+      sum + -percentage * Math.log2(percentage)
     end
-
-    result(info, length)
-  end
-
-  private
-
-  def result(info, total)
-    final = 0
-    info.each do |_symbol, count|
-      next unless count > 0
-      percentage = count.to_f / total
-      final += -percentage * Math.log(percentage) / Math.log(2.0)
-    end
-    final
   end
 end
+
+module ArrayClassification
+  refine Array do
+    def classification
+      collect(&:last)
+    end
+  end
+end
+