what is the lookahead symbol in LL(1) grammar ?

Question

Top down parsers parse LL(K) grammar ,Now if we talk about recursive descent parsers they just scan each input symbol and then perform their respective function calls ,or even LL(1) parsers also see the input symbol and accordingly chose the production and then push the symbols onto stack so then where do they see the look-ahead symbols, I am not getting this .

Answer 1

The input symbol is the look ahead. We would have constructed the parsing table to behave according to the current input symbol. In recursive descent parsers we don't have parsing table hence we need backtracking. Also note that recursive descent parsers also will accept all LL(1) languages.

Comments

LL(k) means left to right top down parser read k symbol at a time

LR(k) means left to right Bottom up parser read k symbol at a time

.

.

---

That's what I am confirming LR deals with right recursive grammars or not ?

---

For a grammer to be LL its should not be left recursive and should not have any conflicts in LL parsing table .
For a grammer to be LR it should not have any conflicts in LR parsing table .
Right recursive grammers are of no interest.for both LL and LR