Re: math_error.7 draft 3, for review

["Michael Kerrisk" <mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>]

Hi Andries,

Reading the POSIX.1 specs of various functions, I see that sometimes
they talk of the return value of a function as being +0, sometimes
+-0, and sometimes -0.  Does one need to care about this?  (e.g., in
updating them man-pages, I'm inclined to group the 0 cases togetehr,
where possible).  If one does need to care, then could you explain to
me why?  Are there cases where one gets bitten by not caring?  (I've
had a browse through the C standard, but I'm not sure that I am yet
any the wiser.)

Hmmm -- just now, I find the Wikipedia article:
http://en.wikipedia.org/wiki/%E2%88%920_(number).  So, are these the
only cases that matter (quoting test from wp):

* using the copysign() function, which is defined by IEEE 754 to copy
the sign of the zero, to some non-zero number
* dividing the number into a positive number—the resulting Infinity
will reflect the sign of the zero.

?

It starts to sound like I should care about postive and negative zero
when rewriting the man pages, or?

Cheers,

Michael
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