为什么这个 C++计算器老是显示错误？

Question

所以我对 C++ 还很陌生，我正在制作一个乘法/除法计算器。当它只是一个操作时，一切都工作正常，但现在它给了我一堆错误

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
    char operation;
    cout << "Select an operation devision(d) multiplication(m)" << endl;
    cin >> operation;

    float firstNumber;
    cout << "Please enter a number ";
    cin >> firstNumber;
  
    float secondNumber;
    cout << "\nEnter a second number ";
    cin >> secondNumber;
    
    float answer; 
        if (operation = m) {
        answer = firstNumber * secondNumber;
        }
        else if (operation = d) {
            answer = firstNumber / secondNumber;
            cout << "\nYour answer is " << showpoint << fixed << setprecision(2) << answer;
        }

    system("pause>0");
}

在底部附近，它根据您输入的操作进行计算，它说有这些错误：

<source>: In function 'int main()':
<source>:19:25: error: 'm' was not declared in this scope; did you mean 'tm'?
   19 |         if (operation = m) {
      |                         ^
      |                         tm
<source>:22:30: error: 'd' was not declared in this scope
   22 |         else if (operation = d) {
      |                              ^
ASM generation compiler returned: 1
<source>: In function 'int main()':
<source>:19:25: error: 'm' was not declared in this scope; did you mean 'tm'?
   19 |         if (operation = m) {
      |                         ^
      |                         tm
<source>:22:30: error: 'd' was not declared in this scope
   22 |         else if (operation = d) {
      |                              ^

Answer 1

主要问题出在语句 if (operation = m) 中，您在其中进行赋值 (=) 而不是比较 (==) 。这也使用（不存在的）变量 m 而不是值 "m" 或 'm'。

一旦你在乘法部分解决了这个问题，你在除法部分也会遇到同样的问题。您也只打印除法部分的输出，但这并不是真正的语法错误，而是逻辑错误。将其移到 if 语句之外以打印答案，无论选择什么操作。