Question

There are mathematical operations that yield real numbers from +/- infinity. For example exp(-infinity) = 0. Is there a standard for mathematical functions in the standard C library that accept IEEE-754 infinities (without throwing, or returning NaN). I am on a linux system and would be interested in such a list for glibc. I could not find such a list in their online manual. For instance their documentation on exp does not mention how it handles the -infinity case. Any help will be much appreciated.

Answer 1

The See Also section of POSIX’ math.h definition links to the POSIX definitions of acceptable domains.

E.g. fabs():

If x is ±0, +0 shall be returned.
If x is ±Inf, +Inf shall be returned.

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I converted mentioned See Also-section to StackOverflow-Markdown:

acos(),
acosh(),
asin(),
atan(),
atan2(),
cbrt(),
ceil(),
cos(),
cosh(),
erf(),
exp(),
expm1(),
fabs(),
floor(),
fmod(),
frexp(),
hypot(),
ilogb(),
isnan(),
j0(),
ldexp(),
lgamma(),
log(),
log10(),
log1p(),
logb(),
modf(),
nextafter(),
pow(),
remainder(),
rint(),
scalb(),
sin(),
sinh(),
sqrt(),
tan(),
tanh(),
y0(),

I contributed search/replace/regex-fu. We now just need someone with cURL-fu.