def p_character_letter(p):
    """character : K_LETTER
                 | K_LETTER K_FROM CHARACTER K_TO CHARACTER
    """
    p[0] = []
    if len(p) == 6:
        char_from = p[3]
        char_to = p[5]
    else:
        char_from = 'a'
        char_to = 'z'
    p[0].append(('letter', (char_from, char_to)))
