Re: bignum branch

[Eli Zaretskii <eliz@gnu.org>]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Fri, 3 Aug 2018 18:22:10 -0700
> Cc: Eli Zaretskii <eliz@gnu.org>, Andy Moreton <andrewjmoreton@gmail.com>,
> 	emacs-devel@gnu.org
> 
> Tom Tromey wrote:
> > Paul> min and max propagate any NaNs they find.
> > 
> > This part I don't understand, since my mental mode of min/max is that
> > they are iteratively applying < or >
> 
> The goal is more to have useful max and min functions than to have a particular 
> implementation tactic. Returning a NaN is more useful, since it warns the caller 
> that the min or max expression doesn't have a reasonable numeric interpretation.

There's a certain tension here between people who are used to do IEEE
compliant FP math in other languages, and the rest of us.  The former
will want the IEEE semantics of NaNs, which is what surprised Tom; the
latter will probably be surprised like Tom was.

I don't see how we can fix this dilemma better than we already did,
with making sure eql compares NaNs as equal.  I do think we should
document the special behavior of NaNs, because many Emacs users will
not be aware of these subtleties.

Thanks.