expm1(3) [redhat man page]

EXPM1(3)						     Linux Programmer's Manual							  EXPM1(3)

NAME

       expm1, log1p - exponential minus 1, logarithm of 1 plus argument

SYNOPSIS

       #include <math.h>

       double expm1(double x);

       double log1p(double x);

DESCRIPTION

       expm1(x)  returns a value equivalent to `exp (x) - 1'. It is computed in a way that is accurate even if the value of x is near zero--a case
       where `exp (x) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal.

       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.

CONFORMING TO

       BSD

SEE ALSO

       exp(3), log(3)

GNU
								    1995-09-16								  EXPM1(3)

EXPM1(3)						     Linux Programmer's Manual							  EXPM1(3)

NAME

       expm1, expm1f, expm1l - exponential minus 1

SYNOPSIS

       #include <math.h>

       double expm1(double x);
       float expm1f(float x);
       long double expm1l(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       expm1(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99
       expm1f(), expm1l(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION

       expm1(x) returns a value equivalent to

	   exp(x) - 1

       It  is  computed in a way that is accurate even if the value of x is near zero--a case where exp(x) - 1 would be inaccurate due to subtrac-
       tion of two numbers that are nearly equal.

RETURN VALUE

       On success, these functions return exp(x) - 1.

       If x is a NaN, a NaN is returned.

       If x is +0 (-0), +0 (-0) is returned.

       If x is positive infinity, positive infinity is returned.

       If x is negative infinity, -1 is returned.

       If the result overflows, a range error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively.

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:

       Range error, overflow
	      An overflow floating-point exception (FE_OVERFLOW) is raised.

       These functions do not set errno.

CONFORMING TO

       C99, POSIX.1-2001.

BUGS

       For some large negative x values (where the function result approaches -1), expm1() raises a bogus underflow floating-point exception.

       For some large positive x values, expm1() raises a bogus invalid floating-point exception in addition to the expected  overflow	exception,
       and returns a NaN instead of positive infinity.

SEE ALSO

       exp(3), log(3), log1p(3)

COLOPHON

       This  page is part of release 3.25 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/.

								    2008-08-05								  EXPM1(3)