ISRO | ISRO CS 2013 | Question 6
Which of the following productions eliminate left recursion in the productions given below: S → Aa | b A → Ac | Sd | ε
(A)
S → Aa | b A → bdA\’ A\’ → A\’c | A\’ba | A | ε
(B)
S → Aa | b A → A\’ | bdA\’, A\’ → cA\’ | adA\’ | ε
(C)
S → Aa | b A → A\’c | A\’d A\’ → bdA\’ | cA | ε
(D)
S → Aa | b A → cA\’ | adA\’ | bdA\’ A\’ → A | ε
Answer: (B)
Explanation:
To remove left recursion from the grammar of the
form : A → Aα | β
We rewrite the production rules as:
A → βA\'
A\'→ αA\'| ε
Given Grammar: S → Aa | b
A → Ac | Sd | ε
after finding indirect left recursion, grammar:
S → Aa | b
A → Ac | Aad | bd | ε
here, α = c, ad, β = bd
So, Grammar after removing left recursion =
S → Aa | b
A → A\' | bdA\'
A\'→ cA\'| ada\'| ε
So, option (B) is correct.
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Last Updated :
26 Apr, 2018
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