Compiler Construction : Timothy G. Griffin

Question

Q5. Find the FIRST and FOLLOW of the grammar to check whether it is LL (1) parser or not.

    N → AB | BA

    A → a | CAC

    B → b | CBC

    C → a | b

Comments

given grammar is not LL(1); first(B)= first(b)$\cap$ first(CBC)=$b\cap(a,b)\neq\phi$

Answer 1

We can see B->b | CBC, will fall into the same cell in the LL(1) Parsing table as first(b)=b and first(C)={a,b}, therefore their intersection is b and hence we have multiple enteries in one cell.
Hence the given grammar is not LL(1)

Comments

can you Explain step by step and write first and follow

Answer 2

Given grammar is ambiguous grammar for string $aabb$. it generates 2 different parse trees for a particular string. For any LL(1) grammar it should be unambiguous grammar. so we can say it is not LL(1) grammar.

1. first(N)={a,b}, follow(N)={$}
2. first(A)={a,b}, follow(A)={$,a,b}
3. first(B)={a,b},follow(B)={$,a,b}
4. first(C)={a,b},follow(C={$,a,b}

Comments

can you Explain step by step and write first and follow