how to remove Circular Dependency in FOLLOW set

Question

Consider a short gramma bellow

S -> Bc | DB
B -> ab | cS
D -> d | epsilon

The FIRST set is

FIRST(S) ={a,c,d}
FIRST(B) = { a,c }
FIRST(D)= { d, epsilon }

in it the

Follow(S)={ Follow(B) }

and

Follow(B) ={ c , Follow(S) }

my question is that how to resolve this circular dependency ?

Answer 1

This circular dependency shouldn't be there to start with. this is the algorithm for finding 'follow's:

Init all follow groups to {}, except S which is init to {$}.
While there are changes, for each A∈V do:
  For each Y → αAβ do:
    follow(A) = follow(A) ∪ first(β)
    If β ⇒* ε, also do: follow(A) = follow(A) ∪ follow(Y)

So in your case, you should get:
Follow(S)={c,$}
Follow(B)={c,$}
Follow(D)={a,c}