程序不知那里错了，各位大侠请帮帮忙！
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <stack>

using namespace std;

double read_and_evaluate(istream& ins);
void evaluate_stack_tops(stack<double>& numbers,stack<char>& operations);
int main()
{
    double answer;
    cout <<"type a arithmetic expression:" <<endl;
    answer = read_and_evaluate(cin);
    cout << "the answer is:" << answer <<endl;

    return EXIT_SUCCESS;
}
double read_and_evaluate (istream& ins)
{
    const char DECIMAL ='.';
    const char RIGHT_PARENTHESIS =')';
    stack<double> numbers;
    stack<char> operations;
    double number;
    char symbol;
    while (ins && ins.peek( ) != '\n')
    {
        if(isdigit(ins.peek( )) || (ins.peek( ) == DECIMAL))
        {
            ins >> number;
            numbers.push(number);
        }
        else if (strchr("+-*",ins.peek( ) != NULL))
        {
            ins >> symbol;
            operations.push(symbol);
        }
        else if (ins.peek( ) == RIGHT_PARENTHESIS)
        {
            ins.ignore( );
            evaluate_stack_tops(numbers,operations);
        }
        else
            ins.ignore();
    }
    return numbers.top( );
}

void evaluate_stack_tops(stack<double>& numbers,stack<char>& operations)
{
    double operand1, operand2;

    operand2 = numbers.top( );
    numbers.pop( );
    operand1 = numbers.top( );
    numbers.pop( );
    switch (operations.top( ))
    {
    case '+': numbers.push(operand1 + operand2);
        break;
    case '-': numbers.push(operand1 - operand2);
        break;
    case '*': numbers.push(operand1 * operand2);
        break;
    case '/': numbers.push(operand1 / operand2);
        break;
    }
    operations.pop( );
}