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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | BUGS | SEE ALSO | COLOPHON |
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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():
_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
These functions return a value equivalent to
log (1 + x)
The result 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
errno is set to EDOM (but see BUGS). An invalid floating-
point exception (FE_INVALID) is raised.
Pole error: x is -1
errno is set to ERANGE (but see BUGS). A divide-by-zero
floating-point exception (FE_DIVBYZERO) is raised.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────┼───────────────┼─────────┤
│log1p(), log1pf(), log1pl() │ Thread safety │ MT-Safe │
└────────────────────────────┴───────────────┴─────────┘
C99, POSIX.1-2001, POSIX.1-2008.
Before version 2.22, the glibc implementation did not set errno to
EDOM when a domain error occurred.
Before version 2.22, the glibc implementation did not set errno to
ERANGE when a range error occurred.
exp(3), expm1(3), log(3)
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2017-09-15 LOG1P(3)
Pages that refer to this page: expm1(3), log(3)
Copyright and license for this manual page
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