now version controlled.

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);
+}