EXPM1Section: Linux Programmer's Manual (3)
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NAMEexpm1, 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)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or
expm1f(), expm1l(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99
DESCRIPTIONexpm1(x) returns a value equivalent to
exp(x) - 1It 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.
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.
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
- 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 3.21 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/.