Re: Suggestion of annex D

[Guillaume Melquiond <guillaume.melquiond@xxxxxxxxxxx>]

Le mardi 29 mai 2007 à 00:08 +1000, Peter Henderson a écrit :

> > Once this clarification is made, the second idea in this suggestion is 
> > that the operation returns NaN for any input on which the function is 
> > undefined. This is the easy consistent option, but it differs from the 
> > C99 standard.
> Disagreeing with the C standard, or any other standard for that matter 
> is the correct choice when they specify bad choices.  The result will be 
> that users will have the choice of the more considered ieee 754 function 
> or an inferior version.

This kind of comment has appeared several times on this mailing-list
lately, and I feel the situation has to be put back into perspective.

On one side, we have a _normative_ annex in an _ISO_ standard, that has
been around for ten years, and that has a big influence on several
widely-used programming languages.

On the other side, we have a _non-normative_ annex in a yet to be
released _non-ISO_ standard, that may suggest to change the behavior of
a few corner cases of a not so obscure function described in the
aforementioned ISO standard.

I think that, if the 754r proposes to change the behavior of pow, this
new function will never even be provided to users. There will not be any
choice available to them. Only the "inferior" version will keep being
provided.

Remark: my point only applies to changing the behavior of an already
standardized function. If the 754r was to define three new functions
(e.g. explog, nth_pow, and nth_root) and if there was no mention of the
pow function, then I am sure the new functions would make their way into
programming language standards.

Best regards,

Guillaume