Re: avoid narrow-to-region (was: Re: replace-regexp)

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

Yuri Khan wrote:

>>> Consistency: If (f a b) returns t once, it must return
>>> t when called again with the same arguments. [...]
>>
>> But here, we want to randomize _every time_.
>
> Every time you do a random shuffle, but not within
> a single shuffle.

Why not?

> A theoretically sound (but still unnecessarily slow)
> sorting-based shuffle would first assign a random weight to
> each line, and then sort by that weight.
>
> But contrast with this:
>
> * Count the lines to be shuffled. Call it N.
> * Generate a random number K_1 from 1 to N. Swap line 1 with line K_1.
> * Generate a random number K_2 from 2 to N. Swap line 2 with line K_2.
> ...
> * Generate a random number K_{N-1} from N-1 to N. Swap line N-1 with
> line K_{N-1}.

DIY Yuri.

> Almost easy enough to put in Elisp

...

> and guarantees uniform distribution (as long as individual
> random indexes are uniformly distributed).

BTW, here is my other stuff, I'm pretty sure it all conforms
to modern-day computer science theory of sorting, but I'll let
you verify it just to be sure.

  https://dataswamp.org/~incal/emacs-init/sort-incal.el

-- 
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