NAME  SYNOPSIS  DESCRIPTION  RETURN VALUE  ERRORS  ATTRIBUTES  CONFORMING TO  SEE ALSO  COLOPHON 

LOG1P(3) Linux Programmer's Manual LOG1P(3)
log1p, log1pf, log1pl  logarithm of 1 plus argument
#include <math.h> double log1p(double x); float log1pf(float x); long double log1pl(long double x); Link with lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): log1p(): _BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 500  _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED  _ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L; or cc std=c99 log1pf(), log1pl(): _BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L; or cc std=c99
log1p(x) returns a value equivalent to log (1 + x) It is computed in a way that is accurate even if the value of x is near zero.
On success, these functions return the natural logarithm of (1 + x). If x is a NaN, a NaN is returned. If x is positive infinity, positive infinity is returned. If x is 1, a pole error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively. If x is less than 1 (including negative infinity), a domain error occurs, and a NaN (not a number) is returned.
See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Domain error: x is less than 1 An invalid floatingpoint exception (FE_INVALID) is raised. Pole error: x is 1 A dividebyzero floatingpoint exception (FE_DIVBYZERO) is raised. These functions do not set errno.
Multithreading (see pthreads(7)) The log1p(), log1pf(), and log1pl() functions are threadsafe.
C99, POSIX.12001.
exp(3), expm1(3), log(3)
This page is part of release 3.65 of the Linux manpages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/manpages/.
20140228 LOG1P(3)
Copyright and license for this manual page