/**
     * Returns {@code true} if the specified number is a
     * Not-a-Number (NaN) value, {@code false} otherwise.
     *
     * @param   v   the value to be tested.
     * @return  {@code true} if the value of the argument is NaN;
     *          {@code false} otherwise.
     */
    public static boolean isNaN(double v) {
        return (v != v);
    }