2 files changed, 28 insertions, 20 deletions

diff --git a/include/expressions.hpp b/include/expressions.hpp
index 604801d..2dcf67c 100644
--- a/include/expressions.hpp
+++ b/include/expressions.hpp
@@ -32,8 +32,7 @@ public:
   virtual ~Expression() = default;
   std::string getRepr();
   virtual Expression *diff(const Differentiator *d) = 0;
-  template <class E>
-  Expression *simplify(E *expr, const Simplifier *s);
+  virtual Expression *simplify(const Simplifier *s) = 0;
   Expression *getLeft();
   Expression *getRight();
   virtual float eval(int arg=0) = 0;
@@ -55,6 +54,7 @@ public:
   ~Literal();
   int getValue();
   float eval(int arg=0) override;
+  Expression *simplify(const Simplifier *s) override;
   Expression *diff(const Differentiator *d) override;
   Expression *copy() override;
 protected:
@@ -70,6 +70,7 @@ public:
   ~Function();
   Expression *getArg();
   float eval(int arg=0) override;
+  Expression *simplify(const Simplifier *s) override;
   Expression *diff(const Differentiator *d) override;
   trig_functions getFunctionName() const;
   Expression *copy() override;
@@ -85,6 +86,7 @@ public:
   explicit Variable(char name);
   ~Variable();
   float eval(int arg=0) override;
+  Expression *simplify(const Simplifier *s) override;
   Expression *diff(const Differentiator *d) override;
   Expression *copy() override;
 protected:
@@ -97,6 +99,7 @@ public:
   ~AddExpression();
   float eval(int arg=0) override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
   Expression *copy() override;
 };
 
@@ -107,6 +110,7 @@ public:
   float eval(int arg=0) override;
   Expression *copy() override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
 };
 
 class NegationExpression : public Expression {
@@ -116,6 +120,7 @@ public:
   float eval(int arg=0) override;
   Expression *copy() override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
 protected:
   void setRepr() override;
 };
@@ -127,6 +132,7 @@ public:
   float eval(int arg=0) override;
   Expression *copy() override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
 };
 
 class MultiplicationExpression : public Expression {
@@ -136,6 +142,7 @@ public:
   float eval(int arg=0) override;
   Expression *copy() override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
 };
 
 class PowerExpression : public Expression {
@@ -145,6 +152,7 @@ public:
   float eval(int arg=0) override;
   Expression *copy() override;
   Expression *diff(const Differentiator *d) override;
+  Expression *simplify(const Simplifier *s) override;
 };
 
 #endif /* EXPRESSIONS_H */
diff --git a/include/simplifier.hpp b/include/simplifier.hpp
index dcc3225..e08f951 100644
--- a/include/simplifier.hpp
+++ b/include/simplifier.hpp
@@ -8,25 +8,25 @@
 
 class Simplifier {
 private:
-  void simplifyChildren(Expression *root, Expression *left, Expression *right);
-  Expression *ruleEval(Expression *expr);
-  Expression *ruleMultiplyByOne(MultiplicationExpression *expr);
-  Expression *ruleDivideByOne(DivisionExpression *expr);
-  Expression *ruleMultiplyByZero(MultiplicationExpression *expr);
-  Expression *ruleZeroDivision(DivisionExpression *expr);
-  Expression *ruleOnePower(PowerExpression *expr);
-  Expression *ruleZeroPower(PowerExpression *expr);
-  Expression *addZero(AddExpression *expr);
+  void simplifyChildren(Expression *root, Expression **left, Expression **right) const;
+  Expression *ruleEval(Expression *expr) const;
+  Expression *ruleMultiplyByOne(MultiplicationExpression *expr) const;
+  Expression *ruleDivideByOne(DivisionExpression *expr) const;
+  Expression *ruleMultiplyByZero(MultiplicationExpression *expr) const;
+  Expression *ruleZeroDivision(DivisionExpression *expr) const;
+  Expression *ruleOnePower(PowerExpression *expr) const;
+  Expression *ruleZeroPower(PowerExpression *expr) const;
+  Expression *addSubstractZero(Expression *expr) const;
 public:
-  Expression *visit(Variable *expr);
-  Expression *visit(Literal *expr);
-  Expression *visit(Function *expr);
-  Expression *visit(NegationExpression *expr);
-  Expression *visit(AddExpression *expr);
-  Expression *visit(SubExpression *expr);
-  Expression *visit(MultiplicationExpression *expr);
-  Expression *visit(DivisionExpression *expr);
-  Expression *visit(PowerExpression *expr);
+  Expression *visit(Variable *expr) const;
+  Expression *visit(Literal *expr) const;
+  Expression *visit(Function *expr) const;
+  Expression *visit(NegationExpression *expr) const;
+  Expression *visit(AddExpression *expr) const;
+  Expression *visit(SubExpression *expr) const;
+  Expression *visit(MultiplicationExpression *expr) const;
+  Expression *visit(DivisionExpression *expr) const;
+  Expression *visit(PowerExpression *expr) const;
 };
 
 Expression *simplify(Expression *to_simplify);