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 mark zeros active zeros mark cons X1 X2 active cons mark X1 X2 mark 0 active 0 mark and X1 X2 active and mark X1 X2 mark tt active tt mark length X active length mark X mark nil active nil mark s X active s mark X cons mark X1 X2 cons X1 X2 cons X1 mark X2 cons X1 X2 cons active X1 X2 cons X1 X2 cons X1 active X2 cons X1 X2 and mark X1 X2 and X1 X2 and X1 mark X2 and X1 X2 and active X1 X2 and X1 X2 and X1 active X2 and X1 X2 length mark X length X length active X length X s mark X s X s active X s X active 1 zeros 0 mark 1 cons 2 0 0 and 2 tt 0 length 1 nil 0 s 1 INNERMOST ./TRS/TRCSR/inn/LengthOfFiniteLists_nosorts_iGM.trs