Exam question ( 9 March 2009)

[Hamid E]

We discussed about this question ( " question 4 : 9 March 2009" ) in
study session, but I think we made a serious mistake. (since we only
talked about conflict in our grammar )


http://www.cse.chalmers.se/edu/course/TIN321/exams/exam-plt-2009-2.pdf

Is your grammar in Question 1 LL(1)? If not, explain why. (3p)

[Oxana Sachenkova]

Yes, this grammar is LL, there are now first/first, first/follow
conflicts and no left recursion. Right?

2011/3/16 Hamid E <hamid...@gmail.com>:

--
Sincerely yours,
Sachenkova Oxana.

[Aarne Ranta]

Hello,

Since conjunction and disjunction are left-associative, your grammar should have left-recursive rules for them, e.g.

  Exp1 ::= Exp1 "&&" Exp2

Then it cannot be an LL grammar (see lecture 4).

The dangling else conflict is another reason for this: a grammar that is not LR(1) cannot be LL(1); the book says more about the relations between these classes. (Notice that an LR conflict always means that the grammar is, strictly speaking, not LR.)

Regards

  Aarne.

[Oxana Sachenkova]

Thank you, Aarne!
Then we was right on the study session, guys.
Just forgot about left recursion.

2011/3/17 Aarne Ranta <aa...@chalmers.se>: