2.7k views

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) edited | 2.7k 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. 0 follow(D)= follow(A). ## 3 Answers +13 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 by Boss (16.3k points) edited 0 Here follow of B is {a,d} not {,a,d}. +1 @Rishav_Bhatt @Ashwani Kumar 2 Why \$$ won't come?

+1
@JEET, $\$$is in follow of$S$& no where we have to calculate follow of$S$while calculating follow of$B$0 Thanks +8 votes Follow of B={d,a} D is right of B so we take terminal first of D that is d if D is € in such case follow of B=follow of A that is a So answer is ad = 31 by Loyal (5.3k points) +2 votes Answer is: 31 1. Here B is in the right side of the Production Rule:$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)

by Junior (841 points)
edited