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():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99
       log1pf(), log1pl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION         top

       log1p(x) returns a value equivalent to

           log (1 + x)

       It 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

   Multithreading (see pthreads(7))
       The log1p(), log1pf(), and log1pl() functions are thread-safe.

CONFORMING TO         top

       C99, POSIX.1-2001.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

                                 2014-02-28                         LOG1P(3)