3 files changed, 26 insertions, 15 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 */
diff --git a/include/expressions.hpp b/include/expressions.hpp
index 3191436..a293408 100644
--- a/include/expressions.hpp
+++ b/include/expressions.hpp
@@ -23,14 +23,14 @@ enum trig_functions {
   i_ctg
 };
 
-class Differentiator; // Forward declaration.
+class Differentiator; // Forward declaration
 
 class Expression {
 public:
   Expression(Expression *left, Expression *right, token_type type);
   virtual ~Expression() = default;
   std::string getRepr();
-  Expression *diff(const Differentiator *d);
+  virtual Expression *diff(const Differentiator *d) = 0;
   Expression *getLeft();
   Expression *getRight();
   virtual float eval(int arg) = 0;
@@ -52,6 +52,7 @@ public:
   ~Literal();
   int getValue();
   float eval(int arg) override;
+  Expression *diff(const Differentiator *d) override;
   Expression *copy() override;
 protected:
   void setRepr() override;
@@ -66,6 +67,7 @@ public:
   ~Function();
   Expression *getArg();
   float eval(int arg) override;
+  Expression *diff(const Differentiator *d) override;
   trig_functions getFunctionName() const;
   Expression *copy() override;
 protected:
@@ -80,6 +82,7 @@ public:
   explicit Variable(char name);
   ~Variable();
   float eval(int arg) override;
+  Expression *diff(const Differentiator *d) override;
   Expression *copy() override;
 protected:
   void setRepr() override;
@@ -90,6 +93,7 @@ public:
   AddExpression(Expression *left, Expression *right);
   ~AddExpression();
   float eval(int arg) override;
+  Expression *diff(const Differentiator *d) override;
   Expression *copy() override;
 };
 
@@ -99,6 +103,7 @@ public:
   ~SubExpression();
   float eval(int arg) override;
   Expression *copy() override;
+  Expression *diff(const Differentiator *d) override;
 };
 
 class NegationExpression : public Expression {
@@ -107,6 +112,7 @@ public:
   ~NegationExpression();
   float eval(int arg) override;
   Expression *copy() override;
+  Expression *diff(const Differentiator *d) override;
 protected:
   void setRepr() override;
 };
@@ -117,6 +123,7 @@ public:
   ~DivisionExpression();
   float eval(int arg) override;
   Expression *copy() override;
+  Expression *diff(const Differentiator *d) override;
 };
 
 class MultiplicationExpression : public Expression {
@@ -125,6 +132,7 @@ public:
   ~MultiplicationExpression();
   float eval(int arg) override;
   Expression *copy() override;
+  Expression *diff(const Differentiator *d) override;
 };
 
 class PowerExpression : public Expression {
@@ -133,6 +141,7 @@ public:
   ~PowerExpression();
   float eval(int arg) override;
   Expression *copy() override;
+  Expression *diff(const Differentiator *d) override;
 };
 
 #endif /* EXPRESSIONS_H */
diff --git a/include/parser.hpp b/include/parser.hpp
index 567ef03..a4e11af 100644
--- a/include/parser.hpp
+++ b/include/parser.hpp
@@ -5,7 +5,7 @@
 #ifndef PARSER_H
 #define PARSER_H
 #include <string>
-#include <vector>
+#include <deque>
 #include "expressions.hpp"
 #include "lexer.hpp"
 
@@ -13,11 +13,11 @@ class Parser{
 private:
   std::string text;
   Lexer tokenizer;
-  std::vector<Expression *> tree_stack;
+  std::deque<Expression *> tree_queue;
   Token var{nil, "{}"};
   void panic();
-  Expression *popStack();
-  Expression *newTree(token_type type);
+  Expression *popQueue();
+  Expression *newTree(token_type type, Expression *left, Expression *right);
   void setText(std::string text);
   void parseExpr();
   void parsePrimeExpr();