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Re: Issue FIXNUM-NON-PORTABLE (Version 3)
- To: masinter.pa%Xerox.COM@Multimax
- Subject: Re: Issue FIXNUM-NON-PORTABLE (Version 3)
- From: Dan L. Pierson <pierson%mist@multimax.ARPA>
- Date: Tue, 01 Nov 88 09:59:55 EST
- Cc: cl-cleanup%sail.stanford.edu@multimax
- In-reply-to: Your message of 31 Oct 88 14:55:00 -0800. <881031-145600-6418@Xerox>
I'm willing to split the issue into two parts, one of which says: constrain
FIXNUM and remove BIGNUM, and the other is to constrain FIXNUM and define
BIGNUM to be exactly (AND INTEGER (NOT FIXNUM)).
In the SUBTYPEP-TOO-VAGUE issue, we should probably make sure the
requirements for FIXNUM and BIGNUM are there.
Here's why I don't like the second proposal:
Consider an implmentation with three numeric representations:
Fast (INTEGER -1024 1023)
Immediate 29 bits
(I understand from the discussion that similar implementations exist.)
Then, with the second proposal:
FIXNUM is Immediate
BIGNUM is (OR Fast Extended) because Fast can't be a FIXNUM.