factorial.c

   1 /*
   2  * factorial: Calculate's a number factorial
   3  */
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6
   7 long double factorial(long n)
   8 {
   9         int i;
  10         long double m;
  11
  12         for (m = 1, i = n; i > 1; i -= 1)
  13                 m *= i;
  14
  15         return m;
  16 }
  17
  18 int main(int argc, char *argv[])
  19 {
  20         long n;
  21         long double f;
  22
  23         if (argc != 2) {
  24                 printf("Usage: %s < number >\n", argv[0]);
  25                 exit(1);
  26         }
  27
  28         n = strtol(argv[1], NULL, 10);
  29         /* FIXME: Error checking */
  30
  31         f = factorial(n);
  32         if (!f) {
  33                 /* FIXME: Explain why */
  34                 fprintf(stderr, "Could not caculate the factorial\n");
  35                 exit(1);
  36         }
  37
  38         printf("%ld! = %Le\n", n, f);
  39
  40         return 0;
  41 }