[bug#60802] [PATCH v3 1/2] platforms: Raise an exception when no suitable platform is found.

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hi Simon,

Simon Tournier <zimon.toutoune@gmail.com> writes:

> Hi,
>
> On mar., 17 janv. 2023 at 09:59, Ludovic Courtès <ludo@gnu.org> wrote:
>> Josselin Poiret <dev@jpoiret.xyz> skribis:
>>
>>> This looks good to me, although in the grand scheme of things I wonder
>>> if that change is a step forward: for those kinds of procedures, we
>>> could expect consumers to instead always properly handle the #f case
>>> themselves, rather than baby-sitting them and systematically relying on
>>> exceptions in the parent procedure, no?  As a caricatural example: the
>>> SRFI-1 `find` could raise an exception instead of returning #f, but I
>>> don't think anyone would consider that proper behaviour.
>>
>> I share this sentiment in general (plus the fact that we should keep UI
>> aspects, such as error reports, separate from core logic).  Here there’s
>> a precedent with other lookup procedures though
>> (‘lookup-bootloader-by-name’, ‘lookup-compressor’,
>> ‘lookup-image-type-by-name’, etc.), so I think it’s okay to keep it that
>> way.
>
> Well, from my small experience with other programming language, they
> barely do return a boolean when they fail.  I think this way using a
> boolean is because some historical reasons when exceptions was not
> implemented in Scheme (or other languages).
>
> Exception allows the motto: «ask for forgiveness, not permission» while
> keeping under control the side effects.  Well, IMHO exception is often a
> good practise for dynamically typed programming language; as Scheme (or
> Python).
>
> From my point of view, exception is not related to “should keep UI
> aspects, such as error reports, separated from core logic”.  This is how
> the exception is handled.  It is often easier to propagate exception
> until an handler than propagate a boolean (as with ’find’).
>
> And if the exception is not handled, then it just returns a backtrace,
> which is more informative, IMHO.

You've summarized well the reasons I think using an exception here makes
sense (and why using exceptions rather than C-style booleans to
propagate error conditions is preferable in general for languages where
it's possible to do so -- luckily Scheme is one).

I'll send a v4 reworking it to use srfi-34/35, so that the discussion to
migrate to (ice-9 exceptions) can be kept separate.

-- 
Thanks,
Maxim