Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!talos!kjones
From: kjones@talos.uu.net (Kyle Jones)
Newsgroups: gnu.emacs.bug
Subject: Re: 24 bit pointers
Message-ID: <1990Jan2.205554.22344@talos.uu.net>
Date: 2 Jan 90 20:55:54 GMT
References: <9001012326.AA04455@atlantis> <32538@news.Think.COM>
Reply-To: kjones@talos.uu.net
Distribution: gnu
Lines: 16

Robert Krawitz writes:
 > I agree with the concept of making integers fast and compact, since
 > they're used often enough so that they shouldn't require a pointer
 > dereference every time.

I'm not so sure it's worth it.  Lisp variable that are used internally
and whose values are normally integers have their values forwarded to
real C ints internally anyway, so there's no overhead except when the
Lisp variables value is changed.  As for the interpreted Lisp, the extra
dereference is small potatoes compared to all the type checking and arg
grokking that goes on while interpreting code.

On the other hand, stealing bits from Lisp ints means dates from the
epoch can't be represented in a single integer.  Thus the file times
returned by file-attributes are difficult to use because relational
operator won't work on them.