double 0 0 double s x s s double x del x nil nil del x cons y xs if eq x y x y xs if true x y xs xs if false x y xs cons y del x xs eq 0 0 true eq 0 s y false eq s x 0 false eq s x s y eq x y first nil 0 first cons x xs x doublelist nil nil doublelist cons x xs cons double x doublelist del first cons x xs cons x xs double 1 0 0 s 1 del 2 nil 0 cons 2 if 4 eq 2 true 0 false 0 first 1 doublelist 1 FULL ./TRS/aprove08/parting02_doublelist.trs