function factory( k, lambda ) {
	if (
		isnan( k ) ||
		isnan( lambda ) ||
		k <= 0.0 ||
		lambda <= 0.0
	) {
		return constantFunction( NaN );
	}
	return quantile;

	/**
	* Evaluates the quantile function for a Weibull distribution.
	*
	* @private
	* @param {Probability} p - input value
	* @returns {number} evaluated quantile function
	*
	* @example
	* var y = quantile( 0.3 );
	* // returns <number>
	*/
	function quantile( p ) {
		if ( isnan( p ) || p < 0.0 || p > 1.0 ) {
			return NaN;
		}
		return lambda * pow( -ln( 1.0 - p ), 1.0/k );
	}
}
Returns a function for evaluating the quantile function for a Weibull distribution.

@param {PositiveNumber} k - shape parameter
@param {PositiveNumber} lambda - scale parameter
@returns {Function} quantile function

@example
var quantile = factory( 2.0, 10.0 );
var y = quantile( 0.4 );
// returns ~7.147

y = quantile( 0.8 );
// returns ~12.686