? adj(b,Y,c(a,c(b,c(b,c(a,emp))))).
Here is a top-down derivation:
yes(Y) <- adj(b,Y,c(a,c(b,c(b,c(a,emp))))). choose clause 3, with {A/b,B/Y,L/c(a,c(b,c(b,c(a,emp)))),F/F1,E/E1} yes(Y) <- ap(F1,c(b,c(Y,E1)),c(a,c(b,c(b,c(a,emp))))) choose clause 2, under {F1/c(a,T2),L/c(b,c(Y,E1)),H/a,R/c(b,c(b,c(a,emp))),T/T2} yes(Y) <- ap(T2,c(b,c(Y,E1)),c(b,c(b,c(a,emp)))) *** choose clause 1 under {T2/emp,Y/b,E1/c(b,c(a,emp))} yes(b) <-