// primeclone.c - Clone of my TI-83+ program

#include <stdio.h>

unsigned long isprime ( unsigned long x );
void factor( unsigned long thenumber );

int main( int argc, char *argv[] )
{
    if (argc < 2)
    {
       puts("Where's my number?");
       return 1;
    }
    
    if (argc > 2)
    {
       puts("It's a factoring program; where are you getting these extra options?");
       return 1;
    }
    
    unsigned long meow;
    
    meow = atoi(argv[1]);
    
    factor( meow );
    
    return 0;
}

unsigned long isprime ( unsigned long x )
{
    unsigned long i = 3, s = sqrt(x);
 
    if (x < 2)
       return 0;
    if (x == 2)
       return 1;
    if (x % 2 == 0)
       return 0;
    
    for ( ; i <= s ; i += 2 )
        if (x % i == 0)
           return 0;
    return 1;
}

void factor( unsigned long thenumber )
{
     unsigned long prime = 2, exp = 0;

     printf ("%u: ", thenumber);

     while( (!isprime(thenumber)) && (thenumber != 1) )
     {
           while( (!(thenumber % prime)) && (thenumber != 1) )
           {
                 thenumber /= prime;
                 exp++;
           }

    if (exp) 
       printf("%u^%u ", prime, exp);
    
    exp = 0;
    while( !isprime(++prime) );
    }
  
    if (thenumber != 1)
       printf("%u^1", thenumber);
    return;
}