man:expm1l
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(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE expm1f(), expm1l(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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 zero--a case where exp(x) - 1 would be inaccurate due to sub- traction 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
allbox; lbw27 lb lb l l l. Interface Attribute Value T{ expm1(), expm1f(), expm1l() T} Thread safety MT-Safe
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
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 float- ing-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 4.16 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
2017-09-15 EXPM1(3)
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