Uses std::cin.ignore() to Keep the User Typing Until the Input Meets the Requirements

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I used to control users' input by making the input a string and process it later. But today, my friend posed this question to me: Can we control input without a char array or string class?

On cppreference.com, I found std::cin.ignore(). This function can help us solve the previous question. Here is an example:

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#include <iostream>
#include <limits>

int main() {
  int n = 0;
  while (true) {
    std::cout << "Please input a number: ";
    std::cin >> n;
    if (!std::cin.good()) {
      std::cerr << "Error input." << std::endl;
      std::cin.clear();
      std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
      continue;
    } else {
      break;
    }
  }
  std::cout << "Your input is: " << n << std::endl;
  return 0;
}