Hi,
Kindly consider the following productions. How can I identify a useless production?

S->aS|A|C
A->a
B->aa
C->aCb

Somebody please guide me.

Zulfi.

 

A production is useless if there is no way for it to ever be used in generating a finite-length string beginning with the start variable.

 

Thanks. Good definition.

Zulfi.