Recently i was studying removal of useless symbols in productions given in Ullman Hopcroft.The grammar goes as followsS-> aAa | aBCA -> aS | bDB - > aBa | bC-> abb | DDD -> aDaIn the explanation that follows, we eliminate D obviously, but the removal of C still baffles me. As D is non generating, but C is both generating and reachable. So why delete C?The resultant grammar is shown as S->aAaA->aSB->aBa | bHere is the link to the photo of the page in the book just in casePage 240: http://tinypic.com/r/17wcw4/8Page 241:http://tinypic.com/r/29w1i82/8
Simplification of CFG
context free;formal grammars