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Circular structures [was Re: IEEE 754 floating-point arithmetic is not completely ordered]

This page is part of the web mail archives of SRFI 67 from before July 7th, 2015. The new archives for SRFI 67 contain all messages, not just those from before July 7th, 2015.



On Apr 16, 2005, at 10:53 AM, Jens Axel Søgaard wrote:

> Bradley Lucier wrote:
>
>> Well, it depends on what your goal is. ...
> Here are some potential goals:
> ...
> 3) default-compare should define a total order on almost all Scheme 
> values

What is "almost all"?  How do a and b compare in the following?

[descartes:~/programs/folding/2] lucier% gsc
loading /usr/local/Gambit-C/gambcext.scm
Gambit Version 4.0 beta 12

 > (define a (cons #f #f))
 > (set-car! a a)
 > (set-cdr! a a)
 > (define b (cons #f #f))
 > (set-car! b b)
 > (set-cdr! b b)
 > (equal? a b)   ;;; doesn't terminate

Is default-compare compatible with equal?

Brad