/// <summary>
/// Checks the letter in the Cipher and the index in the alphabet
/// </summary>
/// <param name="l">the stored letter</param>
/// <param name="i">the stored index</param>
/// <param name="r">the rotor to check</param>
private void RightToLeft(ref char l, ref int i, Rotor r)
{
l = r.LetterInCipher(i);
i = r.AlphaIndexOfLetter(l);
}