Best floating-point questions in December 2011

To infinity and back

Asked on Tue, 06 Dec 2011 by srean c++ c floating-point libc
26 votes

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.

Answered by phresnel

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.

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.