NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON

LOG1P(3)                  Linux Programmer's Manual                 LOG1P(3)

NAME         top

       log1p, log1pf, log1pl -  logarithm of 1 plus argument

SYNOPSIS         top

       #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         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) 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         top

       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         top

       C99, POSIX.1-2001, POSIX.1-2008.

SEE ALSO         top

       exp(3), expm1(3), log(3)

COLOPHON         top

       This page is part of release 4.12 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/.
                                 2016-03-15                         LOG1P(3)

Pages that refer to this page: expm1(3)log(3)