Testing if a number has a decimal value without any library [duplicate]

Answer 1

I think you are looking for something like this:

#include 

int main()
{
  double a;
  std::cin >> a;
  if(int(a) != a)
  {
      std::cout << "decimal";
  }
  else
  {
      std::cout << "no decimal";
  }
  return 0;
}