function pmf( x, N, K, n ) {
	return addon( x, N, K, n );
}
Evaluates the probability mass function (PMF) for a hypergeometric distribution with population size `N`, subpopulation size `K`, and number of draws `n`.

@private
@param {number} x - input value
@param {NonNegativeInteger} N - population size
@param {NonNegativeInteger} K - subpopulation size
@param {NonNegativeInteger} n - number of draws
@returns {Probability} evaluated PMF

@example
var y = pmf( 1.0, 8, 4, 2 );
// returns ~0.571

@example
var y = pmf( 2.0, 8, 4, 2 );
// returns ~0.214

@example
var y = pmf( 0.0, 8, 4, 2 );
// returns ~0.214

@example
var y = pmf( 1.5, 8, 4, 2 );
// returns 0.0

@example
var y = pmf( 2.0, 10, 5, -2 );
// returns NaN

@example
var y = pmf( 2.0, 10, 5, 12 );
// returns NaN

@example
var y = pmf( 2.0, 8, 3, 9 );
// returns NaN