From: "M. Edward (Ed) Borasky" <znmeb@...>
Date: 2006-07-24T02:29:46+09:00
Subject: Re: Infinity

hadley wickham wrote:
>> > Yes, but a lot of languages provide some way of accessing the
>> > "constants" that represent special floating point numbers: Inf, -Inf
>> > and NaN
>> I think Matz vetoed anything that required IEEE floating point a little
>> while ago. So ... for Ruby code to use Inf, -Inf or NaN, there would
>> need to be special care taken to maintain portability.
>
> Thanks for that explanation, although it does worry me a little, I
> understand that getting floating point working precisely correctly
> across multiple platforms is very hard.
Which is *precisely* why dozens of hard core applied mathematicians and 
computer scientists, the IEEE and SIAM (Society for Industrial and 
Applied Mathematics), and nearly every vendor of equipment intended for 
scientific computing, both large and small, developed and embraced the 
IEEE standards! Note that there are actually *two* IEEE standards. The 
one most of us think of is the 32-bit/64-bit one that's implemented in 
Intel hardware. However, there was another looser standard which did not 
specify bit for bit behavior but only the computational requirements. 
The IEEE floating point standards are happy exceptions to the rule that 
nothing good was ever designed by a committee. :)

Some important vendors of such equipment -- Cray, FPS and IBM -- adhered 
to neither of these standards. Digital/Compaq/HP adopted it for the 
Alphas but kept the Vax line at its historic format for compatibility. 
But *new* architectures almost entirely adopted IEEE -- there is little 
reason not to do so. At some point in the evolution of Ruby, the number 
of actual users of non-IEEE platforms will be negligible. Just out of 
curiosity, how many users of non-IEEE Ruby are there on this list, and 
what fraction of the total list membership does that represent? Feel 
free to decline to answer if you're in a classified shop. :)