examples/tutorial/calc.cpp

/**************************************************************************
 *
 * calc.cpp - RPN Calculator -- Illustration of the use of stacks.
 *
 * $Id: //stdlib/dev/examples/stdlib/tutorial/calc.cpp#10 $
 *
 ***************************************************************************
 *
 * Copyright (c) 1994-2005 Quovadx,  Inc., acting through its  Rogue Wave
 * Software division. Licensed under the Apache License, Version 2.0 (the
 * "License");  you may  not use this file except  in compliance with the
 * License.    You    may   obtain   a   copy   of    the   License    at
 * http://www.apache.org/licenses/LICENSE-2.0.    Unless   required    by
 * applicable law  or agreed to  in writing,  software  distributed under
 * the License is distributed on an "AS IS" BASIS,  WITHOUT WARRANTIES OR
 * CONDITIONS OF  ANY KIND, either  express or implied.  See  the License
 * for the specific language governing permissions  and limitations under
 * the License.
 * 
 **************************************************************************/

#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;
}