diff options
Diffstat (limited to 'nonrecurfact.c')
-rw-r--r-- | nonrecurfact.c | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/nonrecurfact.c b/nonrecurfact.c new file mode 100644 index 0000000..3fdbf78 --- /dev/null +++ b/nonrecurfact.c @@ -0,0 +1,58 @@ +/* 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); +} |