calc.cpp

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#include <vector>
#include <stack>
#include <iostream>
 
#include <examples.h>    
 
 
// Simulate the behavior of a simple integer calculator.
 
struct Calculator
{
    int currentMemory () const {
        return data_.top ();
    }
 
    void pushOperand (int value) {
        data_.push (value);
    }
 
    void doOperator (char);
 
private:
 
    std::stack<int, std::vector<int, std::allocator<int> > > data_;
};
 
 
void Calculator::doOperator (char theOp)
{
    int tmp = data_.top ();
    data_.pop ();
 
    switch (theOp) {
    case '+': tmp = data_.top () + tmp; break;
    case '-': tmp = data_.top () - tmp; break;
    case '*': tmp = data_.top () * tmp; break;
    case '/': tmp = data_.top () / tmp; break;
    case '%': tmp = data_.top () % tmp; break;
    }
 
    data_.pop ();
    data_.push (tmp);
}
 
 
int main ()
{
    std::cout << "Calculator example program, from Chapter 8\n"
              << "Enter a legal RPN expression, end with p q (print and quit)"
              << std::endl;
 
    Calculator calc;
 
    for (char c; std::cin >> c; ) {
 
        int intval;
 
        switch (c) {
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
            std::cin.putback (c);
            std::cin >> intval;
            calc.pushOperand (intval);
            break;
        case '+': case '-': case '*': case '/': case '%':
            calc.doOperator (c);
            break;
        case 'p':
            std::cout << calc.currentMemory () << std::endl;
            break;
        case 'q':
            std::cout << "End calculator program" << std::endl;
            return 0;   // quit program
        }
    }
 
    return 0;
}