From ...
From: Erik Naggum <erik@naggum.no>
Subject: Re: A portable DIRECTORY-P. Re: Here we go again. More CMUCL/ACL pathname differences.
Date: 1999/01/15
Message-ID: <3125401498178923@naggum.no>#1/1
X-Deja-AN: 432977763
References: <778kqn$2b2$1@nnrp1.dejanews.com> <3125304296381618@naggum.no> <4n90f53fe0.fsf@rtp.ericsson.se> <3125354057127280@naggum.no> <77mdts$1dlf9@fido.engr.sgi.com>
mail-copies-to: never
Organization: Naggum Software; +47 8800 8879; http://www.naggum.no
Newsgroups: comp.lang.lisp

* rpw3@rigden.engr.sgi.com (Rob Warnock)
| 	* (FILE-NAMESTRING #p"/home/")
| 
| 	""
| 	* (pathname-name #p"/home/")
| 
| 	NIL
| 	* (host-namestring #p"/home/")
| 
| 	"Unix"
| 	* (directory-namestring #p"foo.bar")
| 
| 	""

  I thought we already had the convention that the empty _list_ was
  "nothing", but CMUCL apparently thinks its better to introduce typed
  nothings, like empty strings, too.  sigh.

  so, fine, let's test for the empty string in CMUCL, instead.  it gives
  the function a distinctly Scheme-ish flavor as in (not (null? x)), but
  what the heck, it's free software.

(if #+cmucl (< 0 (length file-namestring))
    #-cmucl file-namestring
  ...)

  the length test would work everywhere, but I want an empty string to be
  _different_ from no string.

#:Erik