function logaddexp( x, y ) {
	var d;
	if ( isnan( x ) || isnan( y ) ) {
		return NaN;
	}
	if ( x === y ) {
		return x + LN2;
	}
	d = x - y;
	if ( d > 0.0 ) {
		return x + log1p( exp( -d ) );
	}
	return y + log1p( exp( d ) );
}
Computes the natural logarithm of \\( \exp(x) + \exp(y) \\).

@param {number} x - input value
@param {number} y - input value
@returns {number} natural logarithm of \\( \exp(x) + \exp(y) \\)

@example
var v = logaddexp( 90.0, 90.0 );
// returns ~90.6931

@example
var v = logaddexp( -20.0, 90.0 );
// returns 90.0

@example
var v = logaddexp( 0.0, -100 );
// returns ~3.7201e-44