 For more complex languages this usually results in very large item sets, which is the reason for the large memory requirements of LR(1) parsers.In our example, the starting symbol requires the nonterminal 'E' which in turn requires 'T', thus all production rules will appear in item set 0.At first, we ignore the problem of finding the lookaheads and just look at the case of an LR(0), whose items do not contain lookahead terminals.