function factory( a, b ) {
	if (
		isnan( a ) ||
		isnan( b ) ||
		a >= b
	) {
		return constantFunction( NaN );
	}
	return quantile;

	/**
	* Evaluates the quantile function for a uniform 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 a + ( p * ( b - a ) );
	}
}
Returns a function for evaluating the quantile function for a uniform distribution with minimum support `a` an maximum support `b`.

@param {number} a - minimum support
@param {number} b - maximum support
@returns {Function} quantile function

@example
var quantile = factory( 2.0, 4.0 );
var y = quantile( 0.4 );
// returns 2.8

y = quantile( 0.8 );
// returns 3.6