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Re: Contagious Inexactness, revision 2

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.

Andrew Wilcox <awilcox@xxxxxxxxxxxxxxxxx> writes:

> Two Scheme implementations returning results flagged as exact, from
> the same computation, performed on the same inputs, will return
> equal values.

I believe this is unimplementable sanely.

Assume, for the sake of argument, that
   (= (expt (sqrt 2) 2) 2)
is an example of an expression which is #t and #f on different
implementations. Of course with your proposal these are inexact

Now consider this:

(define (test)
  (let ((l '()))
    (if (= (expt (sqrt 2) 2) 2)
      (set! l (cons #f l)))
    (length l)))

Does this return an inexact 0 or 1? If yes, how would you implement this?

   __("<         Marcin Kowalczyk
   \__/       qrczak@xxxxxxxxxx
    ^^     http://qrnik.knm.org.pl/~qrczak/