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 Bradley Lucier 17 Oct 2005 22:07 UTC

On Oct 17, 2005, at 4:59 PM, Aubrey Jaffer wrote:

>  | From: Michael Sperber <xxxxxx@informatik.uni-tuebingen.de>
>  | Date: Sun, 16 Oct 2005 21:44:10 -1000
>  |
>  | Aubrey Jaffer <xxxxxx@alum.mit.edu> writes:
>  |
>  | > What is the rationale for mandating exact rationals?
>  |
>  | This (from the SRFI document):
>  |
>  | > Under R5RS, it is hard to write programs whose arithmetic is
>  | > portable across the above categories, and it is unnecessarily
>  | > difficult even to write programs whose arithmetic is portable
>  | > between different implementations in the same category.
>  |
>  | > The portability problems can most easily be solved by requiring
>  | > all implementations to support the full numeric tower.
>
> Easy for who?
>
> Implementing exact non-integers for SCM and Guile would take a lot of
> work.

Implementing exact rationals seemed nearly trivial after the work
needed for a "good" bignum implementation. (104 lines, including
comments and whitespace, for rational +, -, *, /, versus > 2000 lines
for a reasonable set of bignum operations.)

Brad