function exponential2( lambda ) {
		if (
			isnan( lambda ) ||
			lambda <= 0.0
		) {
			return NaN;
		}
		return exponential0( rand, lambda );
	}
Returns a pseudorandom number drawn from an exponential distribution with parameter `lambda`.

@private
@param {PositiveNumber} lambda - rate parameter
@returns {NonNegativeNumber} pseudorandom number

@example
var v = exponential2( 4.8 );
// returns <number>