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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | BUGS | SEE ALSO | COLOPHON |
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EXPM1(3) Linux Programmer's Manual EXPM1(3)
expm1, expm1f, expm1l - exponential minus 1
#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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
expm1f(), expm1l():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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 subtraction of two numbers that are nearly
equal.
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.
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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│expm1(), expm1f(), expm1l() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
C99, POSIX.1-2001, POSIX.1-2008.
Before glibc 2.17, on certain architectures (e.g., x86, but not
x86_64) expm1() raised a bogus underflow floating-point exception
for some large negative x values (where the function result
approaches -1).
Before approximately glibc version 2.11, expm1() raised a bogus
invalid floating-point exception in addition to the expected
overflow exception, and returned a NaN instead of positive
infinity, for some large positive x values.
Before version 2.11, the glibc implementation did not set errno
to ERANGE when a range error occurred.
exp(3), log(3), log1p(3)
This page is part of release 5.13 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/.
2021-03-22 EXPM1(3)
Pages that refer to this page: exp(3), log1p(3)
Copyright and license for this manual page
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