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Linux 2.6 - man page for log1pf (linux section 3)

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

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():
	   _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
       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
       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
	      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.

CONFORMING TO
       C99, POSIX.1-2001.

SEE ALSO
       exp(3), expm1(3), log(3)

COLOPHON
       This  page  is  part of release 3.55 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/.

					    2010-09-20					 LOG1P(3)


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