Re: guile & r5rs

[Radey Shouman <Radey_Shouman@splashtech.com>]

I think the following function does a reasonable
job of dividing two bignums and returning a floating
point result.  It doesn't look as though it
should be too hard to render into C, or to extend
to sqrt and log.

A conservative test for whether something like this is necessary
should also be fairly quick, just look at the number of big digits in
each of the arguments.

(define *float-expt* 1024)  ;; this depends on float representation.
                            ;; probably there should be some way of
                            ;; determining this from the Scheme level.
(define (big-i/ num den)
  (let* ((nf (max 0
                  (- (max (integer-length num)
                          (integer-length den))
                     *float-expt*)))
         (fact/2 (ash 1 (- nf 1))))
    (/ (exact->inexact (ash (+ num fact/2) (- nf)))
       (exact->inexact (ash (+ den fact/2) (- nf))))))