EXPM1
Section: Linux Programmer's Manual (3)
Updated: 2010-09-12
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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 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or
cc -std=c99
expm1f(),
expm1l():
-
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
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
subtraction 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
-
errno
is set to
ERANGE
(but see BUGS).
An overflow floating-point exception
(FE_OVERFLOW)
is raised.
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.
Before version 2.11,
the glibc implementation did not set
errno
to
ERANGE
when a range error occurred.
SEE ALSO
exp(3),
log(3),
log1p(3)
COLOPHON
This page is part of release 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- BUGS
-
- SEE ALSO
-
- COLOPHON
-
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Time: 19:49:21 GMT, April 27, 2011