UGC NET CSE | June 2013 | Part 2 | Question: 22

Question

Given a grammar $S1 \rightarrow Sc, S \rightarrow SA  \mid A, A \rightarrow aSb \mid ab$, there is a rightmost derivation $S1 \Rightarrow Sc \Rightarrow SAC \Rightarrow SaSbc$ Thus, $SaSbc$ is a right sentential form, and its handle is

• A. $SaS$
• B. $bc$
• C. $Sbc$
• D. $aSb$

Answer 1

Handle$:$

            A Handle is a Substring that matches the body of production and whose reduction represents one step along the reverse of the right most derivation.

If we say more precisely $:$

 

 

 

$* \ Source: Ullman$

 

Now the given Right most derivation :

$ S1$ $\Rightarrow$ $Sc$ $\Rightarrow$ $SAC$ $\Rightarrow$ $SaSbc$

Here in the right-sentential form, replacing $aSb$ by $A$ produces the previous right-sentential form. 

So the handle is $A → aSb$

 

Correct Ans : Option D

Answer 2

option D aSb

Comments

What is handle in this context?