(VAR X Y Z X1 X2) (RULES a__dbl(0) -> 0 a__dbl(s(X)) -> s(s(dbl(X))) a__dbls(nil) -> nil a__dbls(cons(X,Y)) -> cons(dbl(X),dbls(Y)) a__sel(0,cons(X,Y)) -> mark(X) a__sel(s(X),cons(Y,Z)) -> a__sel(mark(X),mark(Z)) a__indx(nil,X) -> nil a__indx(cons(X,Y),Z) -> cons(sel(X,Z),indx(Y,Z)) a__from(X) -> cons(X,from(s(X))) mark(dbl(X)) -> a__dbl(mark(X)) mark(dbls(X)) -> a__dbls(mark(X)) mark(sel(X1,X2)) -> a__sel(mark(X1),mark(X2)) mark(indx(X1,X2)) -> a__indx(mark(X1),X2) mark(from(X)) -> a__from(X) mark(0) -> 0 mark(s(X)) -> s(X) mark(nil) -> nil mark(cons(X1,X2)) -> cons(X1,X2) a__dbl(X) -> dbl(X) a__dbls(X) -> dbls(X) a__sel(X1,X2) -> sel(X1,X2) a__indx(X1,X2) -> indx(X1,X2) a__from(X) -> from(X) )