active zeros mark cons 0 zeros active and tt X mark X active length nil mark 0 active length cons N L mark s length L active cons X1 X2 cons active X1 X2 active and X1 X2 and active X1 X2 active length X length active X active s X s active X cons mark X1 X2 mark cons X1 X2 and mark X1 X2 mark and X1 X2 length mark X mark length X s mark X mark s X proper zeros ok zeros proper cons X1 X2 cons proper X1 proper X2 proper 0 ok 0 proper and X1 X2 and proper X1 proper X2 proper tt ok tt proper length X length proper X proper nil ok nil proper s X s proper X cons ok X1 ok X2 ok cons X1 X2 and ok X1 ok X2 ok and X1 X2 length ok X ok length X s ok X ok s X top mark X top proper X top ok X top active X active 1 zeros 0 mark 1 cons 2 0 0 and 2 tt 0 length 1 nil 0 s 1 proper 1 ok 1 top 1 INNERMOST ./TRS/TRCSR/inn/LengthOfFiniteLists_nosorts_C.trs