If there is a production S -> CBD, then everything in FIRST (D) except epsilon is in FOLLOW (B). Place $ in FOLLOW (S), where S is the start symbol. To compute FOLLOW (S) for any non-terminal S, apply the followwing rules until nothing can be added to any FOLLOW set.
#First and follow in compiler design how to#
How to compute follow ( s ) for non-terminal s? Read a character from the input and follow a transition labelled. Calculating First and Follow Solved Examples. 3.15 Fixed-point iteration for calculation of FIRST.
In compiler design, first and follow sets are needed by the parser to properly apply the needed production. Watch video lectures by visiting our YouTube channel LearnVidFun. How to calculate first and follow solved examples? First and Follow Questions with Solutions. Calculating First and Follow Solved Examples. For the start symbol S, place $ in Follow (S). Follow (α) is a set of terminal symbols that appear immediately to the right of α. Similarly, we can make expansion for any production rule X → Y 1 Y 2 Y 3 ….Y n.
So, FOLLOW(S) must contain a.Īlso,as per rule 3, considering the production A->ASD |epsilon and FIRST(D) contains epsilon, we should get FOLLOW(S) = FOLLOW(A).
SO, as you can see from the given grammar,Īs per rule 1, the follow(S) will contains $.Īlso, as per rule 2, S appears in bodies only followed by D( non-terminal), thus, everything except epsilon that is in FIRST(D) must be in FOLLOW(S). Yet.So,should we add FOLLOW(A) too inf FOLLOW(S)? Production is after S production,we have not calculated FOLLOW(A) Trying to calculate FOLLOW(S) which needs FOLLOW(A) in it,but as A If there is a proudction S -> CB, or a production S -> CBD, where FIRST(D) contains epsilon, then everything in FOLLOW(S) is in FOLLOW(B). If there is a production S -> CBD, then everything in FIRST(D) except epsilon is in FOLLOW(B). Place $ in FOLLOW(S), where S is the start symbol. To compute FOLLOW(S) for any non-terminal S, apply the followwing rules until nothing can be added to any FOLLOW set.