|LOG1P(3)||Linux Programmer's Manual||LOG1P(3)|
NAMElog1p, log1pf, log1pl - logarithm of 1 plus argument
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)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
DESCRIPTIONlog1p(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.
RETURN VALUEOn success, these functions return the natural logarithm of (1 + x).
ERRORSSee 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 floating-point exception ( FE_INVALID) is raised.
- Pole error: x is -1
- A divide-by-zero floating-point exception ( FE_DIVBYZERO) is raised.
These functions do not set errno.
CONFORMING TOC99, POSIX.1-2001.
SEE ALSOexp(3), expm1(3), log(3)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.