有没有办法包含多个！=运算符？

Question

I'm trying to make a system that outputs invalid if a variable does not equal whole number or decimal number. The problem is, it outputs invalid when the variable is not equal to the first option instead of both options. Is there a fix for this?

I have tried making it an if statement as well as an else if statement instead of separating them with &&. It did not work.

if (user_input != "whole number") {
    std::cout << "\nInvalid";
    goto label1;
  }
  else if (user_input != "decimal number") {
    std::cout << "\nInvalid";
    goto label1;
  }

It outputs invalid is decimal number is inputted.

Answer 1

Your requirement is that the system should output invalid if the variable does not equal "whole number" or "decimal number".

We can translate this directly into code. To emphasize how I translated the requirement, I'm using and and or , but the code would be identical if you wrote things the more conventional way, using && for and and || for or .

if(user_input != "whole number" and user_input != "decimal number") 
{
    std::cout << "\nInvalid";
    goto label1;
}

Alternatively, we could write:

if (not (user_input == "whole number" or user_input == "decimal number")) 
{
    std::cout << "\nInvalid";
    goto label1;
}

Answer 2

A readable way to do this, with real code:

bool invalid = ((typeid(var) != typeid(int)) && (typeid(var) != typeid(double)));
if(invalid)
    std::cout << "Invalid !" << std::endl;

Hope it helps.