log1p(3) - Linux manual page (original) (raw)
log1p(3) Library Functions Manual log1p(3)
NAME top
log1p, log1pf, log1pl - logarithm of 1 plus argumentLIBRARY top
Math library (_libm_, _-lm_)SYNOPSIS top
**#include <math.h>**
**double log1p(double** _x_**);**
**float log1pf(float** _x_**);**
**long double log1pl(long double** _x_**);**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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
**log1pf**(), **log1pl**():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION top
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 top
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 top
See [math_error(7)](../man7/math%5Ferror.7.html) 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](../man3/errno.3.html)_ is set to **EDOM** (but see BUGS). An invalid floating-
point exception (**FE_INVALID**) is raised.
Pole error: _x_ is -1.
_[errno](../man3/errno.3.html)_ is set to **ERANGE** (but see BUGS). A divide-by-zero
floating-point exception (**FE_DIVBYZERO**) is raised.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **log1p**(), **log1pf**(), **log1pl**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
C11, POSIX.1-2008.HISTORY top
C99, POSIX.1-2001.BUGS top
Before glibc 2.22, the glibc implementation did not set _[errno](../man3/errno.3.html)_ to
**EDOM** when a domain error occurred.
Before glibc 2.22, the glibc implementation did not set _[errno](../man3/errno.3.html)_ to
**ERANGE** when a range error occurred.SEE ALSO top
[exp(3)](../man3/exp.3.html), [expm1(3)](../man3/expm1.3.html), [log(3)](../man3/log.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-11-17 log1p(3)
Pages that refer to this page:expm1(3), log(3)