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Re: implementation categories, exact rationals

This page is part of the web mail archives of SRFI 77 from before July 7th, 2015. The new archives for SRFI 77 contain all messages, not just those from before July 7th, 2015.

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

 | From: Michael Sperber <sperber@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
 | Date: Sun, 16 Oct 2005 21:44:10 -1000
 | Aubrey Jaffer <agj@xxxxxxxxxxxx> 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

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.)