function quantile( p ) {
		if (
			isnan( p ) ||
			p < 0.0 ||
			p > 1.0
		) {
			return NaN;
		}
		return expm1( p * log1p( c ) ) / c;
	}
Evaluates the quantile function for a Bradford distribution.

@private
@param {Probability} p - input value
@returns {number} evaluated quantile function

@example
var y = quantile( 0.3 );
// returns <number>