// ----------------------------------------------------------------------------------- //
/*
  ROOT macro for calculating the first 1000 prime numbers.

  Run this ROOT macro from prompt:
    > root -l PrimeNumbers.c

  Author: Troels C. Petersen (NBI)
  Email:  petersen@nbi.dk
  Date:   29th of August 2012
*/
// ----------------------------------------------------------------------------------- //


//---------------------------------------------------------------------------------- 
void PrimeNumbers()
//---------------------------------------------------------------------------------- 
{
  const int NprimeMax = 1000;                   // Maximum prime number

  // Loop i over numbers from 2 to NprimeMax:
  for (int i=2; i < NprimeMax; i++) {
    bool divisible = false;                    // Define "divisible" (as false)
    int MaxDivisor = int(sqrt(i));             // Define "MaxDivisor"

    // Loop j over numbers from 2 to MaxDivisor:
    for (int j=2; j < MaxDivisor+1; j++) {
      if (i%j == 0) divisible = true;          // Test if i is divisible by j
                                               // ("%" is integer division)
    }
    if (!divisible) printf("  %3d ", i);       // If i is not divisible, then it is a prime
                                               // Print it to the screen using 3 digits
  }
  printf("\n");                                // Print an "end-of-line"
}