LOG1P
Section: Linux Programmer's Manual (3)
Updated: 20170915
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NAME
log1p, log1pf, log1pl  logarithm of 1 plus argument
SYNOPSIS
#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 to
log (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

errno
is set to
EDOM
(but see BUGS).
An invalid floatingpoint exception
(FE_INVALID)
is raised.
 Pole error: x is 1

errno
is set to
ERANGE
(but see BUGS).
A dividebyzero floatingpoint exception
(FE_DIVBYZERO)
is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
Interface  Attribute  Value

log1p(),
log1pf(),
log1pl()
 Thread safety  MTSafe

CONFORMING TO
C99, POSIX.12001, POSIX.12008.
BUGS
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.
SEE ALSO
exp(3),
expm1(3),
log(3)
COLOPHON
This page is part of release 4.15 of the Linux
manpages
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/manpages/.
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 RETURN VALUE

 ERRORS

 ATTRIBUTES

 CONFORMING TO

 BUGS

 SEE ALSO

 COLOPHON

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Time: 17:10:47 GMT, September 22, 2018