c++ - 如何在数组中使用指针？

Question

因此，目前我仍然对使用指针和引用感到困惑，并且我不知道自己在做什么。我的程序是一个计算器，可以存储用户输入的所有内容。有一个选项可以询问用户是否要查看历史记录，是否需要历史记录，程序将显示他/她输入的所有数据。我需要在程序中使用指针和引用，但是我仍然对如何使用指针和数组引用感到困惑
这是我的初始化:

int main() {
  int size = 1, fNum[size], sNum[size];
  char oprtn[size], answer;
  ;
  float result[size];
  int *ptrf = &fNum[size];
  int *ptrs = &sNum[size];
  char *ptro = &oprtn[size];
  float *ptrRes = &result[size];
  while (true) {
    cout << "=====CALCULATOR=====\n\n";
    cout << "ENTER TWO NUMBERS:" << endl;
    while (!(cin >> *ptrf >> *ptrs)) {
      system("cls");
      cout << "INVALID INPUT. PLEASE ENTER TWO NUMBERS:\n";
      cin.clear();
      cin.ignore(2);
    }
    cout << endl;
    do {
      cout << "Choose Operation to be Used: \n"
           << "   +   --- Addition  \n"
           << "   -   --- Subtraction   \n"
           << "   *   --- Multiplication   \n"
           << "   /   --- Division   \n"
           << "   %   --- Remainder   \n";
      cout << "Answer: ";
      cin >> answer;
      cout << endl;
      switch (answer) {
        case '+':
          cout << "ADDITION\n";
          break;
        case '-':
          cout << "SUBTRACTION\n";
          break;
        case '*':
          cout << "MULTIPLICATION\n";
          break;
        case '/':
          cout << "DIVISION\n";
          break;
        case '%':
          cout << "REMAINDER\n";
          break;
        default:
          answer = false;
          system("cls");
          cout << "PLEASE ENTER A VALID ANSWER. CHOOSE BELOW.\n\n";
          cout << "FIRST NUMBER: " << *ptrf << endl;
          cout << "SECOND NUMBER: " << *ptrs;
          cout << endl << endl;
          continue;
      }
    } while (!answer);
    cout << "DO YOU WANT TO TRY AGAIN? (Y / N): ";
    cin >> answer;
    switch (answer) {
      case 'Y':
      case 'y':
        system("cls");
        continue;
      default:
        cout << "VIEW HISTORY? (Y / N): ";
        cin >> answer;
        switch (answer) {
          case 'Y':
          case 'y':
            cout << "HISTORY\n\n";
            break;
          default:
            return 0;
        }
    }
  }
}

Answer 1

这不是有效的C++代码:

  int size = 1, fNum[size], sNum[size];   // wrong: C++ forbids Variable Length Arrays (1)
  char oprtn[size], answer;               // ditto...
  ;
  float result[size];                     // ditto...
  int *ptrf = &fNum[size];         // wrong: this syntax makes ptrf points one past end of array (2)
  int *ptrs = &sNum[size];         // ditto...
  char *ptro = &oprtn[size];       // ditto...

(1):VLA是C语言的概念。一些编译器(gcc和CLang)允许它作为扩展，但是由于标准库中的容器，它在C++中没有用。

(2):初始化指向数组开头的指针的惯用方式只是 int *ptrf = Num;当用作右值(简写为=符号的右侧)时，数组会衰减为指向其第一个元素的指针。因此它读取 (int *) ptr = &(fNum[0]);: ptr是指向 int的指针，其初始值是数组 fNum的第一个元素的地址