implementation categories, exact rationals Aubrey Jaffer (14 Oct 2005 18:29 UTC)
Re: implementation categories, exact rationals John.Cowan (14 Oct 2005 19:26 UTC)
Re: implementation categories, exact rationals Aubrey Jaffer (14 Oct 2005 19:38 UTC)
Re: implementation categories, exact rationals John.Cowan (14 Oct 2005 20:16 UTC)
Re: implementation categories, exact rationals bear (16 Oct 2005 18:08 UTC)
Re: implementation categories, exact rationals Michael Sperber (17 Oct 2005 07:44 UTC)
Re: implementation categories, exact rationals Aubrey Jaffer (17 Oct 2005 21:59 UTC)
Re: implementation categories, exact rationals Bradley Lucier (17 Oct 2005 22:07 UTC)

Re: implementation categories, exact rationals Aubrey Jaffer 14 Oct 2005 19:38 UTC

 | Date: Fri, 14 Oct 2005 15:26:46 -0400
 | From: "John.Cowan" <xxxxxx@reutershealth.com>
 |
 | Aubrey Jaffer scripsit:
 |
 | > What is the rationale for mandating exact rationals?  Over 15 years I
 | > have written numerical Scheme code for everything from symbolic
 | > algebra to Galois fields to linear systems to optics simulations
 | > without needing exact rationals.
 | >
 | > A case could be made if (expt -26. 1/3) returned -2.9624960684073702;
 | > but I know of no Scheme implementation that does so.
 |
 | Why would that be desirable?

Because it is the cube root of -26.  A better example is:
(expt -27 1/3) ==> -3

 | 1.48124803420369+2.5655968538523i
 | (thus Chicken, and Petite Chez just adds a few more significant digits)
 | is a more sensible value.