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From: pepke@gw.scri.fsu.edu (Eric Pepke)
Newsgroups: comp.lang.scheme,comp.lang.lisp
Subject: Re: in defense of C
Message-ID: <542@fsu.scri.fsu.edu>
Date: 8 Mar 90 15:32:50 GMT
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Organization: Florida State University, but I don't speak for them
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References:<1903@skye.ed.ac.uk> <14112@cbnewsc.ATT.COM> <1942@skye.ed.ac.uk>

In article <1942@skye.ed.ac.uk> jeff@aiai.ed.ac.uk (Jeff Dalton) writes:
> You say this as if it were typical of better compilers on machines
> other than SPARCs, such as, maybe, 68020s.  Can they really have safe
> CARs and CDRs, without loss of speed, on a 68020?

I don't know about the internals of any LISP system other than the ones I 
have written.  In the one I am now writing for the 680x0, one can have 
safe CARs and CDRs without loss of speed.  One has to test to see if it is 
(1) a valid list, or (2) NIL, anyway.  So, one just makes that a test for 
(1) a valid list, or (2) anything else.  In my system, that's testing a 
single bit.  In case 1, do the job.  In case 2, return NIL.

Eric Pepke                                    INTERNET: pepke@gw.scri.fsu.edu
Supercomputer Computations Research Institute MFENET:   pepke@fsu
Florida State University                      SPAN:     scri::pepke
Tallahassee, FL 32306-4052                    BITNET:   pepke@fsu

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