expm1(3) - Linux manual page (original) (raw)
expm1(3) Library Functions Manual expm1(3)
NAME top
expm1, expm1f, expm1l - exponential minus 1LIBRARY top
Math library (_libm_, _-lm_)SYNOPSIS top
**#include <math.h>**
**double expm1(double** _x_**);**
**float expm1f(float** _x_**);**
**long double expm1l(long double** _x_**);**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_SOURCEDESCRIPTION top
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.RETURN VALUE top
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 top
See [math_error(7)](../man7/math%5Ferror.7.html) for information on how to determine whether an
error has occurred when calling these functions.
The following errors can occur:
Range error, overflow
_[errno](../man3/errno.3.html)_ is set to **ERANGE** (but see BUGS). An overflow
floating-point exception (**FE_OVERFLOW**) is raised.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **expm1**(), **expm1f**(), **expm1l**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
C11, POSIX.1-2008.HISTORY top
C99, POSIX.1-2001. BSD.BUGS top
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 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 glibc 2.11, the glibc implementation did not set _[errno](../man3/errno.3.html)_ to
**ERANGE** when a range error occurred.SEE ALSO top
[exp(3)](../man3/exp.3.html), [log(3)](../man3/log.3.html), [log1p(3)](../man3/log1p.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 expm1(3)
Pages that refer to this page:exp(3), log1p(3)