regress/roff/de/factorial.in

   1 .Dd December 30, 2014
   2 .Dt FACTORIAL 1
   3 .Os OpenBSD
   4 .Sh NAME
   5 .Nm factorial
   6 .Nd factorial sequence
   7 .Sh DESCRIPTION
   8 .\" recursively calculate a single factorial
   9 .de rfac
  10 .  ie \\$1>1 \{\
  11 .    No \\$1 *
  12 .    nr i \\$1-1
  13 .    rfac \\ni
  14 .    nr acc \\n[acc]*\\$1
  15 .  \}
  16 .  el .nr acc 1
  17 ..
  18 .\" recursively print a sequence of factorials
  19 .de fac
  20 .  No \\$1! =
  21 .  rfac \\$1
  22 .  if \\$1>1 1 =
  23 .  No \\n[acc]
  24 .  if \\$1 \{\
  25 .    br
  26 .    nr i \\$1-1
  27 .    fac \\ni
  28 .  \}
  29 ..
  30 .\" main program
  31 .fac 9