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EXPM1
Section: Linux Programmer's Manual (3)
Updated: 20150419
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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
These functions return a value equivalent to
exp(x)  1
The result is computed in a way that is accurate even if the value of
x
is near
zeroa 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 floatingpoint exception
(FE_OVERFLOW)
is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
Interface  Attribute  Value

expm1(),
expm1f(),
expm1l()
 Thread safety  MTSafe

CONFORMING TO
C99, POSIX.12001, POSIX.12008.
BUGS
For some large negative
x
values (where the function result approaches 1),
expm1()
raises a bogus underflow floatingpoint exception.
For some large positive
x
values,
expm1()
raises a bogus invalid floatingpoint 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 4.04 of the Linux
manpages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
http://www.kernel.org/doc/manpages/.
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 RETURN VALUE

 ERRORS

 ATTRIBUTES

 CONFORMING TO

 BUGS

 SEE ALSO

 COLOPHON

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