// is it "* *" etc. (SNL juxtaposition), or "[]" (NL juxtaposition)?
static boolean isJuxta(Lisp l) {
  if (l == null) ret false;
  if (l.is("[]")) ret true;
  if (l(l.head) == 0) ret false;
  for (int i = 0; i < l(l.head); i++)
    if (l.head.charAt(i) != ((i & 1) == 0 ? '*' : ' '))
      ret false;
  ret true;
}