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Consider the grammar given below:

$S \rightarrow Aa$

$A \rightarrow BD$

$B \rightarrow b \mid \epsilon$

$D \rightarrow d \mid \epsilon$

Let $a,b,d$ and $\$$be indexed as follows:$$\begin{array}{|l|l|l|l|} \hline a & b & d & \$ \\ \hline 3 & 2 & 1 & 0 \\ \hline \end{array}$$Compute the FOLLOW set of the non-terminal B and write the index values for the symbols in the FOLLOW set in the descending order.(For example, if the FOLLOW set is (a,b,d, \) , then the answer should be 3210) asked edited | 2.2k views +1 ad 31 +1 I wrote 13 :/ 0  first() follow() S a,b,d  A b,d,\epsilon a B b, \epsilon a,d D d, \epsilon a 0 how you are getting follow(D) =d ? 0 Corrected. Thanks for correcting me. ## 3 Answers +7 votes Best answer For \text{Follow(B)} \implies \text{First(D)} = \{ \ ,d, \epsilon \} Put \epsilon in II production \text{Follow (B)} = \text{ Follow (A)} = \{ \, a \} \text{Follow (B)} = \{ \, d,a \} According to the question writing Follow set in decreasing order:$$\begin{array}{|l|l|} \hline a & d \\ \hline 3 & 1 \\ \hline \end{array}

Hence $31$ is correct answer
edited

D is right of B so we take terminal first of D that is d if D is € in such case follow of B=follow of A that is a

1. Here B is in the right side of the Production Rule:

$A\rightarrow BD$                 $\therefore FOLLOW(B)= FIRST(D)$

$FIRST(D)=d$ (Therfore it is in $FOLLOW(B)$)

Finally Putting $D\rightarrow \varepsilon$ in the Production $A\rightarrow BD$   then $FOLLOW(B)=FOLLOW(A)$

$FOLLOW(A)=a$ (From the Production rule $S\rightarrow Aa$)

$\therefore FOLLOW(B)= (d,a)$

As we have to write answer in the Decreasing order of INDEX (a,d) $\rightarrow$ (31)

edited

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