Why for A->BC ,Follow of C = Follow of A?

# Why for A->BC ,Follow of C = Follow of A?

**Ruturaj**#2

Follow(B) = First( C )

But you can clearly see that you canâ€™t write Follow( C )=First(anything) as it is the right most literal.

So as per the rules when ever you encounter on the right most literal,

Follow( C )= Follow(A)

**supriyas**#3

I think there is some logic behind,

follow is not just a rule,it helps us in getting a derivation so theres a reason why follow of C = Follow of A for

a production rule like A->BC

**shreya**#4

Suppose in deriving a derivation tree,

u reach upto this point

BC{some string}

so the real cases can be

BCaaa

BCbbbd

BCabbbc

Now you choose to take A->BC at this point.

So the above thing becomes

Aabbbc

so whats Followi actually is you it tells you which terminals can come after a non terminal and though Im not explaining it here how this thing helps us in getting a derivation ,so follow is which terminals can come after a non terminal.

since now we have used A->BC

so whatver comes after A is actually whatver comes after C.

so if you go backwards

Aabbbc

BCabbbc

so thats what follow actaully is the terminals coming after A can come after C so follow of C = follow of A.

Its highly impossible to make understand the complete picture but I hope I was of some help.

Follow is not a rule,

Its a you can say pre computation done which makes our process if whether a string can be deraivable or not process easier.