简单的计算器C++，如何正确地循环和退出？

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我有一个任务来创建一个简单的计算器，但我无法让程序退出;它仍然处于连续循环。我究竟做错了什么？简单的计算器C++，如何正确地循环和退出？

这项任务很简单：编写一个C++程序，使用执行加法，减法，乘法和除法操作的函数（确保覆盖的情况以避免被零除）来模拟基本的计算器。

显示可执行的操作列表的菜单，并从用户那里获得关于他的计算选择的输入。根据用户的操作选择，从用户那里输入号码。假设所有输入值都是double类型的。计算必须使用返回double值的函数来实现。计算结果应显示在屏幕上。

#include <iostream> 
#include <stdlib.h> 
using namespace std; 

double add(double num1, double num2) 
{ 
    return num1 + num2; 
} 

double subtract(double num1, double num2) 
{ 
    return num1 - num2; 
} 

double multiply(double num1, double num2) 
{ 
    return num1 * num2; 
} 

double divide(double num1, double num2) 
{ 
    if (num2 != 0) 
     return num1/num2; 
    else 
     cout << "Invalid entry"; 
} 

int main() 
{ 
    double num1, num2; 
    char operation, q; 

    cout << "Calculator functions:" << endl; 
    cout << "Enter 'm' for Multiplication" << endl; 
    cout << "Enter 'd' for Division" << endl; 
    cout << "Enter 'a' for Addition" << endl; 
    cout << "Enter 's' for Subtraction" << endl; 
    cout << "Select operation or 'q' to quit program" << endl; 
    cin >> operation; 

    do 
    { 
     if (operation == 's' || operation == 'S') 
     { 
      cout << "Enter first number" << endl; 
      cin >> num1; 
      cout << "Enter first number" << endl; 
      cin >> num2; 
      cout << "The difference is " << subtract(num1, num2) << endl; 
     } 

     if (operation == 'a' || operation == 'A') 
     { 
      cout << "Enter first number" << endl; 
      cin >> num1; 
      cout << "Enter first number" << endl; 
      cin >> num2; 
      cout << "The sum is " << add(num1, num2) << endl; 
     } 

     if (operation == 'm' || operation == 'M') 
     { 
      cout << "Enter first number" << endl; 
      cin >> num1; 
      cout << "Enter first number" << endl; 
      cin >> num2; 
      cout << "The product is " << multiply(num1, num2) << endl; 
     } 

     if (operation == 'd' || operation == 'D') 
     { 
      cout << "Enter numerator" << endl; 
      cin >> num1; 
      cout << "Enter denominator" << endl; 
      cin >> num2; 
      cout << "The quotient is " << divide(num1, num2) << endl; 
     } 
     cout << "Select operation or 'q' to quit program" << endl; 
     cin >> operation; 
    } while (operation != 'q' || operation != 'Q'); 
    cout << "Goodbye!" << endl; 
    system("pause"); 
    return 0; 
}

来源

2016-11-30 xeen_1

'而（！操作= 'Q' ||操作= 'Q'）;'=>'而（！操作= 'Q' &&操作= 'Q'）;' –

'operation！='q'|| operation！='Q''对于任何值都是成立的。您应该遵循@πάνταῥεῖ的建议，或者始终将您的输入字符转换为小写字母（或上部字符，您的选择），然后您只需检查单个字符。 –

在附注中 - 您是否考虑过首先将'operation'转换为大写或小写，并跳过所有的OR？ –

更改此：while (operation != 'q' || operation != 'Q');这while (operation != 'q' && operation != 'Q');

您的程序要求cout << "Enter first number" << endl;两次，改变第二个这个cout << "Enter second number" << endl;

，并把这个当用户对输入0来处理的情况下分母：

if (operation == 'd' || operation == 'D') 
     { 
      cout << "Enter numerator" << endl; 
      cin >> num1; 
      cout << "Enter denominator" << endl; 
      cin >> num2; 
      if (num2 != 0) 
      { 
       cout << "The quotient is " << divide(num1, num2) << endl; 
      } 
      else 
      { 
       cout << "You can't devide by zero." << endl; 
      } 
     }

来源

2016-11-30 03:28:46

简单的计算器C++，如何正确地循环和退出？

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