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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | BUGS | SEE ALSO | COLOPHON |
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log1p(3) Library Functions Manual log1p(3)
log1p, log1pf, log1pl - logarithm of 1 plus argument
Math library (libm, -lm)
#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_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 │
└─────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
C99, POSIX.1-2001.
Before glibc 2.22, the glibc implementation did not set errno to
EDOM when a domain error occurred.
Before glibc 2.22, the glibc implementation did not set errno to
ERANGE when a range error occurred.
exp(3), expm1(3), log(3)
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user-space interface documentation) project. Information about
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⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
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⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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2024-06-26. If you discover any rendering problems in this HTML
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part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 log1p(3)
Pages that refer to this page: expm1(3), log(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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