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- To: common-lisp at SU-AI@MIT-MC.ARPA
- Subject: Irrational GCD
- From: Bill Gosper <rwg@NIMBUS.SPA.Symbolics>
- Date: Fri, 28 Dec 84 23:38 PST
- In-reply-to: (failed mail)<841219234502.1.NFEP@NEPONSET.SCRC.Symbolics.COM>
Date: Wednesday, 19 December 1984, 23:45-EST
From: David C. Plummer in disguise <DCP at SCRC-QUABBIN>
[(GCD 1\4 1\3) errs.]
. . .
BTW, the correct answer is 1\12.
Not as far as ZL is concerned. Nor CL for that matter.
Ouch! They must have been jet-lagged at those CL meetings. As
Schroeppel pointed out several millenia back,
(GCD A\B C\D) = (GCD A C)/(LCM B D),
assuming args are in lowest terms. MACSYMA has long known this.
But the absoLULU is further down page 202 of the CL book:
"Mathematically, (lcm) should return infinity." This is so wildly
absurd that I can't even guess the fallacy that led to it. It should
simply be 1.