lib/dydx/algebra/formula.rb in dydx-0.0.4 vs lib/dydx/algebra/formula.rb in dydx-0.0.5

@@ -10,37 +10,50 @@
 
       def differentiate(sym=:x)
         case @operator
         when :+
           f.d(sym) + g.d(sym)
-        when :-
-          f.d(sym) - g.d(sym)
         when :*
           (f.d(sym) * g) + (f * g.d(sym))
-        when :/
-          ((f.d(sym) * g) - (f * g.d(sym)))/(g ^ _(2))
         when :^
           # TODO:
           if f == sym
             g * (f ^ (g - 1))
+          elsif f == e
+            g.d(sym) * self
           else
             self * (g * log(f)).d(sym)
           end
         end
       end
       alias_method :d, :differentiate
 
       def to_s
-        if (subtraction? && f.is_0?) ||
-          (multiplication? && (f.is_minus1? || g.is_minus1?)  )
+        if (multiplication? && (f.is_minus1? || g.is_minus1?)  )
           "( - #{g.to_s} )"
+        elsif multiplication? && g.divisor?
+          "( #{f.to_s} / #{g.x.to_s} )"
+        elsif multiplication? && f.divisor?
+          "( #{g.to_s} / #{f.x.to_s} )"
+        elsif addition? && g.subtrahend?
+          "( #{f.to_s} - #{g.x.to_s} )"
+        elsif addition? && f.subtrahend?
+          "( #{g.to_s} - #{f.x.to_s} )"
         else
           "( #{f.to_s} #{@operator} #{g.to_s} )"
         end
       end
 
       def include?(x)
         f == x || g == x
+      end
+
+      def openable?(x)
+        x.is_num? && (f.is_num? || g.is_num?)
+      end
+
+      def ==(x)
+        to_s == x.to_s
       end
     end
   end
 end
\ No newline at end of file