function factory( alpha, beta ) {
	if (
		isnan( alpha ) ||
		isnan( beta ) ||
		alpha <= 0.0 ||
		beta <= 0.0
	) {
		return constantFunction( NaN );
	}
	return mgf;

	/**
	* Evaluates the moment-generating function (MGF) for a beta distribution.
	*
	* @private
	* @param {number} t - input value
	* @returns {number} evaluated MGF
	*
	* @example
	* var y = mgf( 2.0 );
	* // returns <number>
	*/
	function mgf( t ) {
		if ( isnan( t ) ) {
			return NaN;
		}
		return mgf0( t, alpha, beta );
	}
}
Returns a function for evaluating the moment-generating function (MGF) for a beta distribution with first shape parameter `alpha` and second shape parameter `beta`.

@param {PositiveNumber} alpha - first shape parameter
@param {PositiveNumber} beta - second shape parameter
@returns {Function} MGF

@example
var mgf = factory( 0.5, 0.5 );

var y = mgf( 0.8 );
// returns ~1.552

y = mgf( 0.3 );
// returns ~1.168