/*
 * NFACT -- compute a factorial recursively
 *
 * Usage: nfact n1 n2 .....
 *      
 * Inputs: none
 * Outputs: for each argumenr: n! = f	n as above, f is n!
 * Errors:      - ni < 0
 *
 * Assumptions: - the arguments are not digits followed by non-digits
 *                (unchecked)
 *              - ni >= 0 (checked)
 *      
 * Written by Matt Bishop for ECS 30
 * version 1    November 2, 2015
 */             
#include <stdio.h>      
                        
/*              
 * NFACT -- compute the fqactoriual of n recursively
 * Parameters: n     non-negative integer
 * Returns: n!
 * Assumptions: - n is non-negative integer (not checked)
 * Algorithm: n! = n(n-1)!
 */     
int nfact(int n)
{
	/* base case: 0! = 1 */
	if (n == 0)
		return(1);

	/* recursive case: n! = n * (n-1)! */
	return(n * nfact(n - 1));
}

/*
 * main routine
 */
int main(int argc, char *argv[])
{
	int i;			/* counter in a for loop */
	int n;			/* number to compute the factorial of */
	int badct = 0;		/* number of bad arguments */

	/*
	 * loop through the argument list
	 */
	for(i = 1; i < argc; i++){
		/* translate argument into integer, balk on error */
		if (sscanf(argv[i], "%d", &n) != 1){
			badct++;
			fprintf(stderr, "%s: not an integer\n", argv[i]);
		}
		else if (n < 0)	/* check it is non-negative, balk if not */
			fprintf(stderr, "%d: need a non-negative integer\n", n);
		else		/* compute and print the factorial */
			printf("%d! = %d\n", n, nfact(n));
	}

	/*
	 * return exit code of the number of failures
	 */
	return(badct);
}