|EXPM1(3)||Linux Programmer's Manual||EXPM1(3)|
NAME¶expm1, expm1f, expm1l - exponential minus 1
#include <math.h> double expm1(double x);Link with -lm.
float expm1f(float x);
long double expm1l(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTION¶These functions return a value equivalent to
exp(x) - 1The 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¶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).
|expm1 (), expm1f (), expm1l ()||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 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 4.10 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/.