I thought that way at first. But the program breaks when (getenode znode) is cal...

I thought that way at first. But the program breaks when (getenode znode) is called on an item of type "node", not a list. This happens when (interntimes) takes the path which ends

    (or (setq znode (tellz l node)) (return t))
    (or (eq node (getenode znode)) (zmerge node (getenode znode)))))

and (tellz) has taken the path which ends (return (baserowz* i)). "baserow*" is an array which contains links to "node" items, not list cells. What "z.lisp" and "ze.lisp" are doing, by the way, is solving systems of linear inequalities by using linear programming on a sparse matrix.

Also, see

    (defun isznode (x) (and (hunkp x) (= (hunksize x) 8))) ; original

    (defun isznode (x) (equal (type-of x) 'node))   ; CL version

which indicate that znodes are hunks/structures, not lists. This is inconsistent, yet somehow it used to work.

(If you want to talk privately about this, I'm at "nagle@animats.com". Too much detail for HN.)