function cdf( x ) {
		if ( isnan( x ) ) {
			return NaN;
		}
		return (x < mu) ? 0.0 : 1.0;
	}
Evaluates the cumulative distribution function (CDF) of a degenerate distribution.

@private
@param {number} x - input value
@returns {Probability} evaluated cumulative distribution function

@example
var y = cdf( 10.0 );
// returns <number>