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From: ram@wb1.cs.cmu.edu (Rob MacLachlan)
Newsgroups: comp.lang.lisp
Subject: Re: Floating point in CL?
Message-ID: <10607@pt.cs.cmu.edu>
Date: 29 Sep 90 17:39:15 GMT
References: <TIM.90Sep27140541@watt.cstr.ed.ac.uk>
Distribution: comp
Organization: Carnegie-Mellon University, CS/RI
Lines: 12

Well, one point is that Common Lisp FLOAT is not the same as C float.  If an 
implementation supports more than one floating point format (as I believe 
Allegro does), then a FLOAT declaration is almost useless.  You need to
use SINGLE-FLOAT or DOUBLE-FLOAT, depending on what you have in mind.
Also, Jamie's point about SHORT-FLOAT's being immediate is not true in
all (or even most) Lisp's on conventional hardware.

You should also make sure your non-float arithmetic is getting open-coded,
i.e. all your DOTIMES variables should be declared FIXNUM.  And any arrays
should be declared to be SIMPLE-ARRAY or whatever.

  Rob