from X cons X from s X first 0 Z nil first s X cons Y Z cons Y first X Z sel 0 cons X Z X sel s X cons Y Z sel X Z from 1 1 cons 2 1 s 1 1 first 2 1 2 0 0 nil 0 sel 2 1 2 FULL ./TRS/CSR/Ex1_Luc02b.trs