Hello,

To continue a tangent, if adding an explicit isnan() makes the code run any
slower, I think you should file a bug with GCC to get that fixed.

In general, I really dislike the idea of adjusting coding style to work
around a compiler's limitations. If the compiler is broken, I think it's
best to fix it and move on.

Thanks,
Noah Lavine


On Mon, Mar 25, 2013 at 10:53 AM, Eli Zaretskii <eliz@gnu.org> wrote:

> > Date: Mon, 25 Mar 2013 07:35:51 -0700
> > From: Paul Eggert <eggert@cs.ucla.edu>
> > CC: schwab@linux-m68k.org, Emacs-devel@gnu.org
> >
> > On 03/25/2013 01:20 AM, Eli Zaretskii wrote:
> >
> > > Out of fairness, you introduced this style into Emacs sources
> >
> > I've certainly used it in the changes I made, and as a result it's
> > become more popular, but I did not introduce it.  That style has
> > been used in Emacs, as a minority style, for many years.
>
> AFAIR, it was once a negligible minority at best, so much so that I
> don't remember it being used.  That was in the days that the only
> style enforced in the Emacs sources was what the GNU Coding Standards
> say, btw.  That's what allowed "minority styles" in the first place.
>
> > > If we want our code to be robust in the face of NaNs, we should
> > > probably use 'isnan' explicitly
> >
> > That will slow the code down and make it harder to read.
>
> I disagree; there's nothing unclear in a call to isnan, and the
> slow-down is negligible, if it exists at all, and won't be noticed in
> the context of Emacs, which doesn't pretend to be a fast
> number-cruncher anyway.
>
> > Perhaps a
> > comment could be introduced; but must we really add a comment
> > "watch out for NaNs!" every time we have a floating point comparison?
>
> Such comments would be even worse.
>
> But the problem with relying on 0 < foo is that most people won't even
> consider the subtle difference between that and !(foo >= 0) when NaNs
> are involved.  Calling isnan makes that explicit.
>
> Anyway, this issue is tangential to the style issue.
>
>