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1 point by byronsalty 4509 days ago | link | parent

In practice I imagine one would just use a known symbol like 'removed mid list/tree instead of blindly using a nil. But this is much less fun.

2 points by kennytilton 4508 days ago | link

Puzzled. Do you mean the nils would arise because non-nil entries would be changed to nil as they were (somehow) processed? Just delete the cons:

   (= (cdr prior-kill-me) (cdr kill-me))
instead of:

   (= (car kill-me) nil)
Otherwise you are forever iterating over the now irrelevant cons,