function factory( alpha, beta ) {
	var betaLogCDF;
	if (
		isnan( alpha ) ||
		isnan( beta ) ||
		alpha <= 0.0 ||
		beta <= 0.0
	) {
		return constantFunction( NaN );
	}
	betaLogCDF = betaFactory( alpha, beta );
	return logcdf;

	/**
	* Evaluates the natural logarithm of the cumulative distribution function (CDF) for a beta prime distribution.
	*
	* @private
	* @param {number} x - input value
	* @returns {number} evaluated logCDF
	*
	* @example
	* var y = logcdf( 2.0 );
	* // returns <number>
	*/
	function logcdf( x ) {
		if ( isnan( x ) ) {
			return NaN;
		}
		if ( x <= 0.0 ) {
			return NINF;
		}
		if ( x === PINF ) {
			return 0.0;
		}
		return betaLogCDF( x / ( 1.0 + x ) );
	}
}
Returns a function for evaluating the natural logarithm of the cumulative distribution function (CDF) for a beta prime 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} logCDF

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

var y = logcdf( 0.8 );
// returns ~-0.767

y = logcdf( 0.3 );
// returns ~-1.143