GNU bug report logs - #58812
[PATCH] Add '--symlink' to 'guix shell'

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: zimoun <zimon.toutoune <at> gmail.com>
Cc: Ludovic Courtès <ludo <at> gnu.org>, 59164 <at> debbugs.gnu.org, 58812 <at> debbugs.gnu.org
Subject: [bug#58812] [bug#59164] Coding style: similarly-named variables
Date: Mon, 21 Nov 2022 15:55:46 -0500

Hi Simon,

zimoun <zimon.toutoune <at> gmail.com> writes:

> Hi Maxim,
>
> On Fri, 18 Nov 2022 at 12:02, Maxim Cournoyer <maxim.cournoyer <at> gmail.com> wrote:
>
>> The intent was to keep away from the following imperative style, which
>> hurts both readability and debuggability in my opinion:
>>
>> --8<---------------cut here---------------start------------->8---
>> (let* ((my-target "something")
>>        (my-target (mutate-once my-target))
>>        (my-target (mutate-twice my-target)))
>>  (do-something-with my-target))
>> --8<---------------cut here---------------end--------------->8---
>
> Well, ’mutate-*’ is not really mutating.  Maybe I miss something and
> from my understanding, this ’let*’reads,
>
> (let ((my-target "something"))
>   (let ((my-target (mutate-once my-target)))
>     (let ((my-target (mutate-twice my-target)))
>       (do-something-with my-target))))
>
>
> and not,
>
> (begin
>   (define my-target "something")
>   (set! my-target (mutate-once my-target))
>   (set! my-target (mutate-twice my-target))
>   (do-something-with my-target))

Right.  I used "mutated" where I should have used "shadowed by lexical
scoping".  The outcome for me is the same; the original value of an
argument (target) in the code gets shadowed, thus is theory it becomes
more difficult to inspect its original value, should we have a debugger
that is able to stop at the place to inspect to print ',locals'.

In practice since using breakpoints/a debugger to debug Guile code
rarely works as intended (in my experience hacking on Guix!), we
typically sprinkle the source with 'pk', and that point becomes moot.

> Well, the former is ’lexical-scope’d so the 3 ’my-target’ are not truly
> an imperative style, I guess.
>
> Back to the pattern, you are suggesting to write,
>
> (let* ((my-target "something")
>        (my-target* (mutate-once my-target))
>        (my-target** (mutate-twice my-target*)))
>   (do-something-with my-target**))

> well, I am not convinced it helps for readibility.  And I think, the
> pattern is manually doing what ’let*’ is already doing for you.

The value it provides is that it becomes easy to inspect each
intermediary result in a debugger.

I think we're done expressing the arguments to have on both sides, which
aren't too strong either ways :-).  I'm happy to restrain myself using
such a pattern and keep moving forward.

-- 
Thanks,
Maxim

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