YES TRS: active(and(true(),X)) -> mark(X) active(and(false(),Y)) -> mark(false()) active(if(true(),X,Y)) -> mark(X) active(if(false(),X,Y)) -> mark(Y) active(add(0(),X)) -> mark(X) active(add(s(X),Y)) -> mark(s(add(X,Y))) active(first(0(),X)) -> mark(nil()) active(first(s(X),cons(Y,Z))) -> mark(cons(Y,first(X,Z))) active(from(X)) -> mark(cons(X,from(s(X)))) mark(and(X1,X2)) -> active(and(mark(X1),X2)) mark(true()) -> active(true()) mark(false()) -> active(false()) mark(if(X1,X2,X3)) -> active(if(mark(X1),X2,X3)) mark(add(X1,X2)) -> active(add(mark(X1),X2)) mark(0()) -> active(0()) mark(s(X)) -> active(s(X)) mark(first(X1,X2)) -> active(first(mark(X1),mark(X2))) mark(nil()) -> active(nil()) mark(cons(X1,X2)) -> active(cons(X1,X2)) mark(from(X)) -> active(from(X)) and(mark(X1),X2) -> and(X1,X2) and(X1,mark(X2)) -> and(X1,X2) and(active(X1),X2) -> and(X1,X2) and(X1,active(X2)) -> and(X1,X2) if(mark(X1),X2,X3) -> if(X1,X2,X3) if(X1,mark(X2),X3) -> if(X1,X2,X3) if(X1,X2,mark(X3)) -> if(X1,X2,X3) if(active(X1),X2,X3) -> if(X1,X2,X3) if(X1,active(X2),X3) -> if(X1,X2,X3) if(X1,X2,active(X3)) -> if(X1,X2,X3) add(mark(X1),X2) -> add(X1,X2) add(X1,mark(X2)) -> add(X1,X2) add(active(X1),X2) -> add(X1,X2) add(X1,active(X2)) -> add(X1,X2) s(mark(X)) -> s(X) s(active(X)) -> s(X) first(mark(X1),X2) -> first(X1,X2) first(X1,mark(X2)) -> first(X1,X2) first(active(X1),X2) -> first(X1,X2) first(X1,active(X2)) -> first(X1,X2) cons(mark(X1),X2) -> cons(X1,X2) cons(X1,mark(X2)) -> cons(X1,X2) cons(active(X1),X2) -> cons(X1,X2) cons(X1,active(X2)) -> cons(X1,X2) from(mark(X)) -> from(X) from(active(X)) -> from(X) linear polynomial interpretations on N: active_A(x1) = x1 active#_A(x1) = x1 and_A(x1,x2) = x1 + x2 + 3 and#_A(x1,x2) = x1 + x2 + 5 true_A = 0 true#_A = 0 mark_A(x1) = x1 mark#_A(x1) = x1 + 4 false_A = 0 false#_A = 2 if_A(x1,x2,x3) = x1 + x2 + x3 + 5 if#_A(x1,x2,x3) = x1 + x2 + x3 + 5 add_A(x1,x2) = x1 + x2 + 3 add#_A(x1,x2) = 6 0_A = 2 0#_A = 1 s_A(x1) = 1 s#_A(x1) = 3 first_A(x1,x2) = x1 + x2 + 6 first#_A(x1,x2) = 7 nil_A = 1 nil#_A = 0 cons_A(x1,x2) = 1 cons#_A(x1,x2) = 6 from_A(x1) = 7 from#_A(x1) = 3 precedence: add > active > false = if > and = mark > true = 0 = s = first = from > nil = cons