tfb at tfeb.org
Mon Dec 7 15:27:37 PST 2009
On 7 Dec 2009, at 22:36, Paul Krueger wrote:
> I guess I would have expected that if the ":from-end t" was honored
> that #'plusp would never be called on the 'a element, but obviously
> that isn't the case.
At a slight tangent: is there a way to implement such a search, on a
list, efficiently? By "efficiently" I mean something like "without
doing something equivalent to making a copy of the list". Obviously
it is easy to do this on anything with fast random access, but I can't
see a way on a list.
The two ways I can see of doing it are: making a backwards copy of the
list, or recursing (but not tail-recursing) down it and doing the
tests on the way back up. Is there any other approach?
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