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From: barmar@kulla (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: fill-pointers and initial-contents in Common Lisp
Message-ID: <31009@news.Think.COM>
Date: 20 Oct 89 20:25:42 GMT
References: <2013@xyzzy.UUCP>
Sender: news@Think.COM
Distribution: usa
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 20

In article <2013@xyzzy.UUCP> ledford@berlin.rtp.dg.com () writes:
>I have a question about the make-array function in Common Lisp as
>defined in "Common Lisp the Language" by Guy L. Steele Jr.  If a
>non-nil fill-pointer is specified along with an initial-contents
>value, can only the active part of the array be initialized or 
>do both the active and inactive parts have to be initialized.
>I can't find where Steele addresses this situation.

The fill pointer is only used by functions that the documentation
specifically says use it.  Since the MAKE-ARRAY documentation doesn't say
anything about only the active portion being initialized, it must be the
entire thing.  In general, the fill pointer is only used by sequence and
string functions; the fill pointer exists primarily to allow vectors to be
used to implement growable sequences with performance comparable to that of
lists.  Most functions that operate on arrays of any rank ignore the fill
pointer.
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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