Path: utzoo!utgpu!watmath!clyde!ima!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: Bugs in Lucid?
Message-ID: <35944@think.UUCP>
Date: 31 Jan 89 22:40:18 GMT
References: <6150@columbia.edu>
Sender: news@think.UUCP
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 32

In article <6150@columbia.edu> djk@vail.cs.columbia.edu (David Kurlander) writes:
>This past week I started to use some of Common Lisp's advanced array
>features, sometimes achieving quite unexpected results.  I think that
>I've stumbled upon two bugs in Lucid Common Lisp, but there's a small
>chance that I might be using displaced offsets incorrectly.  I would
>appreciate it if a CommonLisp guru could tell me whether the former or
>latter is true.

I think your examples were fine, and that Lucid is in error.  I also
tried both your examples on a Symbolics 3640, and it produced the
results I expected.

Here's another one that I noticed while trying your second example:

(setq u (make-array 20 :element-type 'string-char :fill-pointer t)
      y (make-array 5 :element-type 'string-char :displaced-to u
		    :displaced-index-offset 6 :fill-pointer t)
      *print-array* t
      *print-circle* t)
(replace u "Common Lisp")
(setf (fill-pointer u) 11)
(list y u) => (#1=" Lisp" "Common Lisp")
(list u y) => ("Common Lisp" #1=" Lisp")

This is mostly just weird, since it doesn't actually produce any
incorrect results.

Barry Margolin
Thinking Machines Corp.

barmar@think.com
{uunet,harvard}!think!barmar