Core Python Programming (2nd Edition)

The following code represents our library of C functions which we want to wrap so that we
can use this code from within the Python interpreter. main() is our tester function.
1 #include
2 #include
3 #include
4
5 int fac(int n)
6 {
7 if (n < 2) return(1); /* 0! == 1! == 1 */
8 return (n)*fac(n-1); /* n! == n*(n-1)! */
9 }
10
11 char *reverse(char *s)
12 {
13 register char t, /* tmp */
14 *p = s, /* fwd */
15 *q = (s + (strlen(s)-1)); /* bwd */
16
17 while (p < q) /* if p < q */
18 { /*swap & mv ptrs */
19 t = *p;
20 *p++ = *q;
21 *q-- = t;
22 }
23 return s;
24 }
25
26 int main()
27 {
28 char s[BUFSIZ];
29 printf("4! == %d\n", fac(4));
30 printf("8! == %d\n", fac(8));
31 printf("12! == %d\n", fac(12));
32 strcpy(s, "abcdef");
33 printf("reversing 'abcdef', we get '%s'\n", \
34 reverse(s));
35 strcpy(s, "madam");
36 printf("reversing 'madam', we get '%s'\n", \
37 reverse(s));
38 return 0;
39 }
The last piece of code is the required main() function. We use it to be our tester, sending various
arguments to fac() and reverse() . With this function, we can actual tell whether our code works (or
not).
Now we should compile the code. For many versions of Unix with the gcc compiler, we can use the
following command:
$ gcc Extest1.c -o Extest
$