forward is f ( n --> n )

  [ dup 0 = if done
    dup 1 - recurse f - ] is m ( n --> n )

  [ dup 0 = iff 1+ done
    dup 1 - recurse m - ]
                    resolves f ( n --> n )

  say "f = "
  20 times [ i^ f echo sp ] cr
  say "m = "
  20 times [ i^ m echo sp ] cr