1.\" $OpenBSD: factorial.in,v 1.2 2017/07/04 14:53:27 schwarze Exp $
2.Dd $Mdocdate: July 4 2017 $
3.Dt FACTORIAL 1
4.Os
5.Sh NAME
6.Nm factorial
7.Nd factorial sequence
8.Sh DESCRIPTION
9.\" recursively calculate a single factorial
10.de rfac
11.  ie \\$1>1 \{\
12.    No \\$1 *
13.    nr i \\$1-1
14.    rfac \\ni
15.    nr acc \\n[acc]*\\$1
16.  \}
17.  el .nr acc 1
18..
19.\" recursively print a sequence of factorials
20.de fac
21.  No \\$1! =
22.  rfac \\$1
23.  if \\$1>1 1 =
24.  No \\n[acc]
25.  if \\$1 \{\
26.    br
27.    nr i \\$1-1
28.    fac \\ni
29.  \}
30..
31.\" main program
32.fac 9
33