Creating FIRST and FOLLOW sets for all non-terminals

Question

If somebody could help me with the rules of FIRST and FOLLOW sets that would be awesome.

The question is calculate the FOLLOW sets for all of the non-terminals in the following grammar

S ::= S b T a E ¦ a T b ¦ c T a c     R ::= E T ¦ a E

T ::= a c E ¦ epsilon                 E ::= R ¦ T a d ¦ epsilon

I have read the rules of creating follow sets and understood the basic examples but I am confused at what I should be doing when I write FIRST(S) for this

any help would be greatly appreciated.

Answer 1

Are you talking about the FIRST1 sets? You simply build a set of all nonterminals, that may be at the beginning of a derivation.

Consider the right-hand side of S: every derivation of S starts with the S, a, c, so FIRST1(S) = FIRST1(S) union {a, c} = {a, c}.