(C++) Prime, how to check if a number is prime

include <iostream>

include <cassert>


bool IsPrime(const int x)
{
  for (int i=2; i<x; ++i)
  {
    if (x % i == 0) return false;
  }
  return true;
}
int main()
{
  //Check if it works
  assert(IsPrime(1)==true);
  assert(IsPrime(2)==true);
  assert(IsPrime(3)==true);
  assert(IsPrime(4)==false);
  assert(IsPrime(5)==true);
  assert(IsPrime(6)==false);
  assert(IsPrime(7)==true);
  assert(IsPrime(8)==false);
  assert(IsPrime(9)==false);
  assert(IsPrime(10)==false);
  assert(IsPrime(11)==true);
  //Ask the user for a value
  std::cout << "Please enter a number: ";
  int anyNumber = -1;
  std::cin >> anyNumber;
  const bool isPrime = IsPrime(anyNumber);
  if (isPrime == true)
  {
    std::cout << "The number is prime." << std::endl;
  }
  else
  {
    std::cout << "The number is not a prime." << std::endl;
  }
}

bool IsPrime(const int x)
{
  //Only positive numbers are prime
  if(x <= 0) { return false; }
  //1 and 2 are prime (although if 1 is prime can be debated)
  if(x < 3) { return true;  }
  //Even numbers are not prime
  if(x % 2 == 0) { return false; }
  const int halfX = x/2;
  for (int i=3; i<halfX; i+=2)
  {
    if (x % i == 0) return false;
  }
  return true;
}

Code links

• assert
• bool
• cassert (header file)
• const
• cin, std::cin
• cout, std::cout
• endl, std::endl
• false
• for
• int
• main
• return
• std::cin
• std::cout
• std::endl
• true