DEFUN ("other-buffer", Fother_buffer, Sother_buffer, 0, 3, 0,
       doc: /* Return most recently selected buffer other than BUFFER.
Buffers not visible in windows are preferred to visible buffers, unless
optional second argument VISIBLE-OK is non-nil.  Ignore the argument
BUFFER unless it denotes a live buffer.  If the optional third argument
FRAME specifies a live frame, then use that frame's buffer list instead
of the selected frame's buffer list.

The buffer is found by scanning the selected or specified frame's buffer
list first, followed by the list of all buffers.  If no other buffer
exists, return the buffer `*scratch*' (creating it if necessary).  */)
  (Lisp_Object buffer, Lisp_Object visible_ok, Lisp_Object frame)
{
  struct frame *f = decode_live_frame (frame);
  Lisp_Object tail = f->buffer_list, pred = f->buffer_predicate;
  Lisp_Object buf, notsogood = Qnil;

  /* Consider buffers that have been seen in the frame first.  */
  for (; CONSP (tail); tail = XCDR (tail))
    {
      buf = XCAR (tail);
      if (candidate_buffer (buf, buffer)
	  /* If the frame has a buffer_predicate, disregard buffers that
	     don't fit the predicate.  */
	  && (NILP (pred) || !NILP (call1 (pred, buf))))
	{
	  if (!NILP (visible_ok)
	      || NILP (Fget_buffer_window (buf, Qvisible)))
	    return buf;
	  else if (NILP (notsogood))
	    notsogood = buf;
	}
    }

  /* Consider alist of all buffers next.  */
  FOR_EACH_LIVE_BUFFER (tail, buf)
    {
      if (candidate_buffer (buf, buffer)
	  /* If the frame has a buffer_predicate, disregard buffers that
	     don't fit the predicate.  */
	  && (NILP (pred) || !NILP (call1 (pred, buf))))
	{
	  if (!NILP (visible_ok)
	      || NILP (Fget_buffer_window (buf, Qvisible)))
	    return buf;
	  else if (NILP (notsogood))
	    notsogood = buf;
	}
    }

  if (!NILP (notsogood))
    return notsogood;
  else
    {
      AUTO_STRING (scratch, "*scratch*");
      buf = Fget_buffer (scratch);
      if (NILP (buf))
	{
	  buf = Fget_buffer_create (scratch);
	  Fset_buffer_major_mode (buf);
	}
      return buf;
    }
}