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Re: "The starting list count" ?????
From: |
Alan Mackenzie |
Subject: |
Re: "The starting list count" ????? |
Date: |
Mon, 3 Jan 2022 19:21:33 +0000 |
Hello, Stefan.
On Mon, Jan 03, 2022 at 13:05:23 -0500, Stefan Monnier wrote:
> > .. What does this mean, please? What does "is the starting list count"
> > mean? There is only one "list", so what is the "list count"?
> I'm not sure how to define it in general, but:
> (let ((x (list 1 2 3 4 5 6 7))) (setf (nthcdr 5 x) (nthcdr N x)) x)
> returns a list with a #N inside of it (well, for N sufficiently small
> to make sense here, obviously).
> AFAIK this is only used to avoid inf-looping, but if/when you actually
> care about that you should use `print-circle` which additionally
> preserves sharing and gives an output that's more explicit about
> what's going on, and hence easier to understand (tho not necessarily
> easier to read).
I might have understood it now. I think (1 . #1) refers to:
----------------- ---
| | | |
| v v |
-----------------------+-------- ---------+-----------------------
| | | | | | | |
| | | | | | | |
| | | | | | | |
| 1 | | | | | | nil |
| | | | | |
| | | | | |
| | | | | |
-------------------------------- ---------------------------------
Am I right? This is an ugly thing, which surely only the most twisted of
imaginations could conceive. ;-)
Obviously, a depth first operation on this "list" is going to take a long
time.
Just as a matter of interest, this object is being passed to
macroexp-strip-symbol-positions during the byte compilation of
seq-tests.el.
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
- "The starting list count" ?????, Alan Mackenzie, 2022/01/03
- Re: "The starting list count" ?????, Stefan Monnier, 2022/01/03
- Re: "The starting list count" ?????,
Alan Mackenzie <=
- Re: "The starting list count" ?????, Stefan Monnier, 2022/01/03
- Re: "The starting list count" ?????, Stefan Monnier, 2022/01/03
- Re: "The starting list count" ?????, Alan Mackenzie, 2022/01/03
- Re: "The starting list count" ?????, Stefan Monnier, 2022/01/03
- Re: "The starting list count" ?????, Alan Mackenzie, 2022/01/03
- Re: "The starting list count" ?????, Stefan Monnier, 2022/01/03
Re: "The starting list count" ?????, Andreas Schwab, 2022/01/03