function pmf( x ) {
		if ( isnan( x ) ) {
			return NaN;
		}
		if ( x === 0.0 ) {
			return 1.0 - p;
		}
		if ( x === 1.0 ) {
			return p;
		}
		return 0.0;
	}
Evaluates the probability mass function (PMF) for a Bernoulli distribution.

@private
@param {number} x - input value
@returns {Probability} evaluated PMF

@example
var y = pmf( 2.0 );
// returns <number>