1 files changed, 11 insertions, 9 deletions
diff --git a/include/differentiator.hpp b/include/differentiator.hpp
index f14f2d5..cef5211 100644
--- a/include/differentiator.hpp
+++ b/include/differentiator.hpp
@@ -14,15 +14,17 @@ private:
   Expression *ptr;
 public:
   Differentiator();
-  Expression *visit(Literal *expr);
-  Expression *visit(Variable *expr);
-  Expression *visit(Function *expr);
-  Expression *visit(NegationExpression *expr);
-  Expression *visit(AddExpression *expr);
-  Expression *visit(SubExpression *expr);
-  Expression *visit(DivisionExpression *expr);
-  Expression *visit(MultiplicationExpression *expr);
-  Expression *visit(PowerExpression *expr);
+  Expression *visit(Literal *expr) const;
+  Expression *visit(Variable *expr) const;
+  Expression *visit(Function *expr) const;
+  Expression *visit(NegationExpression *expr) const;
+  Expression *visit(AddExpression *expr) const;
+  Expression *visit(SubExpression *expr) const;
+  Expression *visit(DivisionExpression *expr) const;
+  Expression *visit(MultiplicationExpression *expr) const;
+  Expression *visit(PowerExpression *expr) const;
 };
 
+Expression *deriv(Expression *to_deriv);
+
 #endif /* DIFFERENTIATOR_H */