a compelling yarn , but not quite a ripping one 
(ROOT (NP (NP (DT a) (JJ compelling) (NN yarn)) (, ,) (CC but) (RB not) (PDT quite) (NP (DT a) (NN ripping) (CD one))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (, ) (CC ) (RB ) (PDT ) (NP (DT ) (NN ) (CD ))))