expression client

visitors.cpp

class expression_t
{
public:
    virtual int accept(expression_visitor &v) = 0;
    virtual ~expression_t() {}
};
using expression = unique_ptr<expression_t>;

class type_number : public expression_t
{
    int value_;

public:
    type_number(int v) :
        value_(v)
    {
    }

    type_number(string v) :
        value_(stoi(v))
    {
    }

    int get() const
    {
        return value_;
    }

    int accept(expression_visitor &v)
    {
        return v.visit_number(*this);
    }
};

class binary_expression : public expression_t
{
    expression left_;
    expression right_;
    char oper_;

    public:
    binary_expression(expression l,
                      expression r,
                      char o) :
        left_(move(l)),
        right_(move(r)),
        oper_(o)
    {
    }

    expression_t *left()
    {
        return left_.get();
    }

    expression_t *right()
    {
        return right_.get();
    }

    char operation() const
    {
        return oper_;
    }

    int accept(expression_visitor &v)
    {
        return v.visit_binary(*this);
    }
};