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- To: guy.steele@cmu-10a
- Subject: elementary functions
- From: Kim.fateman at Berkeley
- Date: Thu, 24 Dec 1981 02:48:00 -0000
- Cc: Kim.jkf@UCB-C70, gjc@MIT-MC, griss@utah-20, jonl@MIT-MC, masinter@PARC-MAXC, rpg@SU-AI
I have no objection to making lisp work better with numerical computation.
I think that it is a far more complicated issue than you seem to think
to put in elementary functions. Branch cuts are probably not hard.
APL's notion of a user-settable "fuzz" is gross. Stan Brown's
model of arithmetic is (Ada notwithstanding) inadequate as a prescriptive
model (Brown agrees). If you provide a logarithm function, are you
willing to bet that it will hold up to the careful scrutiny of people
As for the vagaries of arithmetic in Franz, I hope such things will
get ironed out along with vagaries in the Berkeley UNIX system. Kahan
and I intend to address such issues. I think it is a mistake to
address such issues as LANGUAGE issues, though.
I have not seen Penfield's article (yet).
As for the rational number implementation question, it seems to me
that implementation of rational numbers (as pairs) loses little by
being programmed in Lisp. Writing bignums in lisp loses unless you
happen to have access to machine instructions like 64-bit divided by
32 bit, from Lisp.
I would certainly like to see common lisp be successful; if you
have specific plans for the arithmetic that you wish to get comments and/or
help on, please give them a wider circulation. E.g. the IEEE
floating point committee might like to see how you might incorporate
good ideas in a language.
I would be glad to pass your plans on to them.