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