lib/dydx/algebra/formula.rb in dydx-0.0.3 vs lib/dydx/algebra/formula.rb in dydx-0.0.4

@@ -35,8 +35,12 @@
           "( - #{g.to_s} )"
         else
           "( #{f.to_s} #{@operator} #{g.to_s} )"
         end
       end
+
+      def include?(x)
+        f == x || g == x
+      end
     end
   end
 end
\ No newline at end of file