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Suppose we have a rightmost derivation which proceeds as follows:
$\begin{array}{ccc}S &\rightarrow & Aabw \\ & \rightarrow &ABw \end{array}$
Which of the following is a possible handle for it?

  1. $\begin{array}{ccc} A &\rightarrow & ab \end{array}$
  2. $\begin{array}{ccc} A &\rightarrow & a \end{array}$
  3. $\begin{array}{ccc} S &\rightarrow & A \end{array}$
  4. $\begin{array}{ccc} B &\rightarrow & ab \end{array}$
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2 Answers

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Best answer
Ans is D .

Handle is part of the string in sentential form that will be reduced to non-terminal i.e left hand side of a production

In the above derivation, sentential form Aabw is reduced to ABw so has to be a production with B --> ab and that is the handle at this point of derivation.
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A handle is a reduction that would allow future reductions to reach back to the start symbol. We only want to reduce at handles in Bottom Up Parsing.

Here, $B\rightarrow ab$ is a handle. Because by doing so, we reach $Aabw$, through which we finally reach S.

Option D


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