expm1, expm1f, expm1l - exponential minus 1
#include <math.h>Link with -lm.
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():_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
expm1f(), expm1l():_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
expm1(x) returns a value equivalent toIt is computed in a way that is accurate even if the value of x is near zeroa case where exp(x) - 1 would be inaccurate due to subtraction of two numbers that are nearly equal.
exp(x) - 1
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 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.
exp(3), log(3), log1p(3)
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