|EXPM1(3)||Linux Programmer's Manual||EXPM1(3)|
NAMEexpm1, expm1f, expm1l - exponential minus 1
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)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
DESCRIPTIONexpm1(x) returns a value equivalent to
exp(x) - 1
It 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 VALUEOn success, these functions return exp(x) - 1.
ERRORSSee 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.
CONFORMING TOC99, POSIX.1-2001.
BUGSFor some large negative x values (where the function result approaches -1), expm1() raises a bogus underflow floating-point exception.
SEE ALSOexp(3), log(3), log1p(3)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.