Common wisdom on arithmetic (IEEE)

[Pascal Bourguignon]

> On 3 Nov 2018, at 13:26, Antoniotti Marco <antoniotti.marco at disco.unimib.it> wrote:
> 
> 
> 
>> On Nov 3, 2018, at 24:54 , Bob Cassels <bobcassels at netscape.net> wrote:
>> 
>> Of course they are represented internally the same way other floating point values are.
>> 
>> Are you asking how to print those values? (Print -0.0 like that. Print + and - infinity some way they can be read by the reader. Preferably some way that's not otherwise a legal token. Probably print NaNs using the #unreadable syntax. I don't remember how that works. I don't remember what we did at Symbolics, even though I'm probably the one who did it. I can ask around, if you care.) Or something else?
> 
> Thank you.
> 
> I do not really care about printing and reading NaNs and it looks like most implementations do read and write IEEE infinities.
> 
> Th problem is that ANSI does not talk about infinities and NaNs, so the issue I have is what to do with them in a “portable” library (YMMV).
> 
> I was toying with the idea of using symbolic constants for infinities, but it looks like using IEEE infinities directly is a better - and simpler - way to follow.

Note that there are a big number of NANs.  If you want to print them readably, you definitely need a syntax able to deal with all of them, not just a couple of infinities.


-- 
__Pascal J. Bourguignon__




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