lib/dydx/algebra/formula.rb in dydx-0.0.5 vs lib/dydx/algebra/formula.rb in dydx-0.0.6

@@ -49,11 +49,30 @@
 
       def openable?(x)
         x.is_num? && (f.is_num? || g.is_num?)
       end
 
+      # TODO: interchangeable
       def ==(x)
         to_s == x.to_s
+      end
+
+      def common_factors(formula)
+        nil unless formula.is_a?(Formula)
+        if f == formula.f
+          [:f, :f]
+        elsif g == formula.g
+          [:g, :g]
+        elsif f == formula.g
+          [:f, :g]
+        elsif g == formula.f
+          [:g, :f]
+        end
+      end
+
+      def commutate!
+        @f, @g = @g, @f
+        self
       end
     end
   end
 end
\ No newline at end of file