active from X mark cons X from s X active length nil mark 0 active length cons X Y mark s length1 Y active length1 X mark length X active from X from active X active cons X1 X2 cons active X1 X2 active s X s active X from mark X mark from X cons mark X1 X2 mark cons X1 X2 s mark X mark s X proper from X from proper X proper cons X1 X2 cons proper X1 proper X2 proper s X s proper X proper length X length proper X proper nil ok nil proper 0 ok 0 proper length1 X length1 proper X from ok X ok from X cons ok X1 ok X2 ok cons X1 X2 s ok X ok s X length ok X ok length X length1 ok X ok length1 X top mark X top proper X top ok X top active X active 1 from 1 mark 1 cons 2 s 1 length 1 nil 0 0 0 length1 1 proper 1 ok 1 top 1 FULL ./TRS/TRCSR/Ex14_AEGL02_C.trs