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Date: Mon, 21 Jun 2021 18:27:02 +0200
Message-ID: <CAOwTYAvmGVvKn8zJEr--pLSDwL3_AuEn_daEiP-PMLZAQBhb4g@mail.gmail.com>
To: =?UTF-8?Q?Bj=C3=B6rn_Larsson?= <bjorn.x.larsson@telia.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, PHP internals <internals@lists.php.net>, 
	Larry Garfield <larry@garfieldtech.com>
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Subject: Re: [PHP-DEV] [Vote] Partial Function Application
From: krakjoe@gmail.com (Joe Watkins)

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I'd like to note a couple of things ...

The behaviour of nullsafe and strict types being unspecified in the RFC
would allow us to solve those problems later.

The behaviour of strict types right now is objectively wrong, the partial
takes strictness from the application site, so as Nikita already knew when
he asked the question; calls from a non-strict file will not behave as you
expect.

With regard to the complexity in the implementation: I think it's important
to understand that the complexity of the implementation is a product of the
semantics we landed on during discussion.

The first implementation where we only had ? was technically simpler, but
not intuitive from a user perspective.

Now we have semantics that are easy to understand, that you can communicate
in a few lines. But the implementation is necessarily complicated as a
result of those semantics.

We also have to remember that this is actually some kind of middle ground,
it's not the most complicated version of partial application we could have
- because that most complicated version would also include support for
re-ordering parameters (named placeholders), and nor is it the simplest
which offloaded a lot of (cognitive) overhead onto the programmer.

The question is not can we simplify the implementation, the question is
rather, is the necessary complexity of an implementation with the kind of
semantics that are desirable justified.

Cheers
Joe




On Mon, 21 Jun 2021 at 16:26, Bj=C3=B6rn Larsson via internals <
internals@lists.php.net> wrote:

> Den 2021-06-18 kl. 16:08, skrev Nikita Popov:
> > On Wed, Jun 16, 2021 at 6:17 PM Larry Garfield <larry@garfieldtech.com>
> > wrote:
> >
> >> Hi folks.  The vote for the Partial Function Application RFC is now
> open,
> >> and will run until 30 June.
> >>
> >> https://wiki.php.net/rfc/partial_function_application
> >>
> >> Of particular note, a few people had asked about using ...? instead of
> ...
> >> for the variadic placeholder.  In the end we decided not to explore
> that,
> >> as Nikita explained off-list it was actually more confusing, not less,
> as
> >> it would suggest "placeholder for a variadic" rather than "a placehold=
er
> >> that is variadic."  Otherwise, it's just more typing.  The syntax
> choices
> >> section of the RFC has been updated accordingly.
> >>
> >
> > A couple of notes on the content (or non-content) of the RFC:
> >
> > * The behavior of nullsafe calls with PFA has been brought up in the
> > discussion, but is not mentioned in the RFC. For reference, $foo?->bar(=
?)
> > is the same as $foo !=3D=3D null ? $foo->bar(?) : null. I don't think t=
he
> > behavior is particularly unreasonable, but I also think it's not
> > particularly useful and may be surprising (in that there is a plausible
> > alternative behavior). I think you may have been better off forbidding
> that
> > case.
> >
> > * The behavior of parameter names / reflection with regard to variadic
> > parameters is very odd. For function test(...$args) and test(?, ?, ?) y=
ou
> > get back a function that nominally has three parameters with the name
> > $args. Parameter names in PHP are generally required to be unique, and =
of
> > course this also has implications for named arguments, for example this
> > works, while it probably shouldn't:
> > https://3v4l.org/cQITD/rfc#focus=3Drfc.partials To be honest, I'm not s=
ure
> > what the right way to handle this is, but I don't think this is it. A
> > possibility would be to bring back the concept of name-less parameters =
we
> > had prior to PHP 8 (for internal functions only), or possibly to make t=
he
> > signature less precise by simply retaining an ...$args parameter, and
> just
> > making the enforcement of "at least three parameters" an implementation
> > detail. The latter seems like the best option.
> >
> > * The RFC doesn't specify how PFA interacts with strict types. If I
> create
> > a partially-applied function in strict_types=3D1 file and call it in a
> > strict_types=3D0 file, what happens? Will it use strict_types=3D0 seman=
tics,
> > including for arguments that were bound in the strict_types=3D1 file?
> >
> > * It's worth noting that the "new Foo(?)" syntax will create and destro=
y
> a
> > Foo object as part of creating the partial (not just a call to the
> > partial). I've mostly convinced myself that this is *probably* harmless=
.
> It
> > would have interacted negatively with an earlier version of
> > https://wiki.php.net/rfc/new_in_initializers, but I think the problem
> there
> > was not on the side of partials.
> >
> > In any case, I'm voting no on this one: While PFA is simple on a
> conceptual
> > level, the actual proposal is complex and has lots of tricky edge cases=
.
> > Especially once you take a look at the implementation. I'm not convince=
d
> > that PFA in its full generality is justified for inclusion in PHP.
> >
> > Regards,
> > Nikita
> >
> Would you look on this feature in a different light if the above
> concerns about strict types and nullsafe calls could be clarified /
> solved? Or is it about the implementation with it's complexity and
> tricky edge cases?
>
> I myself think one should take into account that this is a feature
> that would make PHP stand out even more. Not being a follower of
> other languages here :-)
>
> Regards //Bj=C3=B6rn L
>
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