Re: O(N^2) behavior in LOOP

[Lennart Borgman]

On Sun, May 30, 2010 at 12:06 AM, Daniel Colascione
<address@hidden> wrote:
> On 5/29/10 5:56 PM, Daniel Colascione wrote:
>> Before I go fix the loop macro, is there a _reason_ for the nconc silliness?
>
> Err, never mind. LOOP has to work that way. An 'into' variable is
> visible; code that LOOP knows nothing about can modify it in arbitrary
> ways, which would invalidate any cached tail pointer, ruling out that
> approach. Also, code that inspects the variable should see a
> representation "as it should be", which rules out a temporarily-reversed
> representation, ruling out the push and nconc used in the
> anonymous-variable case.
>
> I don't see any way to do better than what LOOP does now without some

Perhaps advice against using it and give alternatives?