expm1

expm1 - Exponential of e minus 1

float expm1( float $x )

expm1() raises e to the power of x and subtracts 1. The calculation is done in a way such that the result is accurate even if the value of x is near zero.

Parameters:

x - The exponent. It can be a scalar or an array.

Return Value:

exp( x ) - 1. If x is an array, the return value will also be an array.

Notes:

On platforms where expm1() is absent from the standard C library (i.e. Windows), expm1() is approximated using a first order Taylor expansion when x is near zero:

if(fabs(x) < 1e-5) {
	return x + 0.5 * x * x;
} else {
	return exp(x) - 1.0;
}

Version

1.0 and above.