blob: 3fdbf787cd6ebea10e49c5169d78a0367a6d667f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
/* non-recursive factorial */
#include <u.h>
#include <libc.h>
void
printdec(int n)
{
char s[16], *p;
int r;
p = s+16;
*--p = '\n';
for(;;){
r = n%10;
*--p = '0'+r;
n /= 10;
if(n == 0 || p == s)
break;
}
write(1, p, s+sizeof(s)-p);
}
int
fact(int n)
{
int a;
a = n;
repeat:
if(n <= 0)
return 0;
else if(n == 1)
return a;
a *= --n;
goto repeat;
}
void
usage(void)
{
fprint(2, "usage: %s n\n", argv0);
exits("usage");
}
void
main(int argc, char *argv[])
{
int n;
ARGBEGIN{
default: usage();
}ARGEND;
if(argc != 1)
usage();
n = strtol(argv[0], nil, 0);
printdec(fact(n));
exits(0);
}
|
