Other Alias
log1pf, log1plSYNOPSIS
#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():
-
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
log1pf(), log1pl():
-
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions return a value equivalent tolog (1 + x)The result is computed in a way that is accurate even if the value of x is near zero.
RETURN VALUE
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.
ERRORS
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 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
log1p(), log1pf(), log1pl() | Thread safety | MT-Safe |
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.COLOPHON
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