Actions of A LR-Parser : 1. Shift s -- shifts the next input symbol and the state s onto the stack ( S o X 1 S 1 ... X m S m , a i a i+1 ... a n $ ) ⇒ ( S o X 1 S 1 ... X m S m a i s, a i+1 ... a n $ ) 2. Reduce A→ b (or r n where n is a production number) Pop 2| b | (=r) items from the stack; Then push A and s where s=goto[s m-r ,A] ( S o X 1 S 1 ... X m S m , a i a i+1 ... a n $ ) ⇒ ( S o X 1 S 1 ... X m-r S m-r A s, a i ... a n $ ) Output is the reducing production reduce A→ b 3. Accept – Parsing successfully completed 4. Error -- Parser detected an error (an empty entry in the action table).