Comments on: distinguishing usual numbers, infinities and NaN http://uucode.com/blog/2007/05/30/distinguishing-usual-numbers-infinities-and-nan/ advocating olpa's open source developments Thu, 20 Nov 2008 09:06:33 +0000 http://wordpress.org/?v=2.2.3 By: olpa http://uucode.com/blog/2007/05/30/distinguishing-usual-numbers-infinities-and-nan/#comment-8280 olpa Fri, 01 Jun 2007 02:51:55 +0000 http://uucode.com/blog/2007/05/30/distinguishing-usual-numbers-infinities-and-nan/#comment-8280 I've got an e-mail reply from Kalle Olavi Niemitalo <kon iki fi>: -- Apparently R5RS does not require support for infinities, but if there is such support, I think these should work: (define (nan? x) (not (= x x))) (define (inf? x) (and (nan? (- x x)) (not (nan? x)))) I like how there are no numerals in these. -- It's a nice idea, I didn't thought about it. Unfortunately, SISC interpreter has a bug. (= (/ 0.0 0.0) (/ 0.0 0.0)) is #t.</kon> I’ve got an e-mail reply from Kalle Olavi Niemitalo :

–
Apparently R5RS does not require support for infinities,
but if there is such support, I think these should work:

(define (nan? x) (not (= x x)))
(define (inf? x) (and (nan? (- x x)) (not (nan? x))))

I like how there are no numerals in these.
–

It’s a nice idea, I didn’t thought about it.

Unfortunately, SISC interpreter has a bug. (= (/ 0.0 0.0) (/ 0.0 0.0)) is #t.

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