First time here? Checkout the FAQ!
+2 votes
Consider the following parse tree:

                          /    |    \     
                 string    +     string
                /    |    \              |
       string     -    string      2
           |                 |
           9                5

Which of the following statement is true?

(A) Both + and - are having equal precendence

(B) + is having higher precedence

(C) - is having higher precedence

(D) None of these
asked in Compiler Design by Active (1.6k points)   | 186 views

2 Answers

+7 votes
Best answer
See the task is easier here than if the grammar were given and then asked that which operator has more precedence.But here we can answer about the precedence by simply examining the dervation tree.The behaviour is similar to recursion tree if you recall

According to the tree , we know that calling is done in top down manner but execution is done in bottom up manner.So the '-' being lower in the tree will be executed first then the '+' which is at higher level.

So '-' has higher precedence than '+'.

Hence C) is correct option.
answered by Veteran (65.9k points)  
selected by
dats what m confused....but the grammar is ambiguous na...u r seeing according to this instance of parse tree only?
what if S->S-S/S+S was given?

both - and + are on same level...but again since it is ambiguous how can we decide about precedence?
Ya it is an ambiguous grammar but it is not of concern since in this case - and + will be in same level of the derivation tree although the derivation tree is not unique.
0 votes
Option C will be right option for it.

The operator having low level have higher precedence compare to operator having low level.

That's option C will be right option for.
answered by Loyal (4.6k points)  

Related questions

0 votes
0 answers
asked in Compiler Design by thor Boss (8.6k points)   | 154 views
0 votes
1 answer
asked in Compiler Design by Rakesh K Active (1.6k points)   | 50 views
+2 votes
1 answer

Top Users Apr 2017
  1. akash.dinkar12

    3518 Points

  2. Divya Bharti

    2558 Points

  3. Deepthi_ts

    2040 Points

  4. rude

    1966 Points

  5. Tesla!

    1768 Points

  6. Shubham Sharma 2

    1610 Points

  7. Debashish Deka

    1608 Points

  8. Arunav Khare

    1464 Points

  9. Arjun

    1430 Points

  10. Kapil

    1424 Points

Monthly Topper: Rs. 500 gift card

22,076 questions
28,047 answers
24,137 users