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Date: Fri, 18 Oct 2019 15:45:13 -0400
In-Reply-To: <CABdc3WqEzFV4ytrVtJB8OS2=3VMuNsHR7MqsTAHsg8-U==CkWA@mail.gmail.com>
Cc: David Rodrigues <david.proweb@gmail.com>,
 PHP Internals List <internals@lists.php.net>
To: =?utf-8?Q?Micha=C5=82_Brzuchalski?= <michal.brzuchalski@gmail.com>
References: <CAEsg9X0Tmkzxz9x2KgwNbPNdbmMz=a0J7Rt84Lh10W=3GQpRkA@mail.gmail.com>
 <CABdc3WqEzFV4ytrVtJB8OS2=3VMuNsHR7MqsTAHsg8-U==CkWA@mail.gmail.com>
Subject: Re: [PHP-DEV] Inline switch as alternative to nested inline
 conditional
From: mike@newclarity.net (Mike Schinkel)

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> On Oct 15, 2019, at 11:33 PM, Micha=C5=82 Brzuchalski =
<michal.brzuchalski@gmail.com> wrote:
>=20
> I have an RFC in draft for that and planning to finish it soon =
together
> with some syntax optimisations - you can see it at
> https://wiki.php.net/rfc/switch-expression-and-statement-improvement
>=20
> Cheers,
> Micha=C5=82 Brzuchalski

In an earlier message I said I would return to comment on some concerns =
I have with the RFC.

In general, I would appreciate having a way to express a "switch" in an =
expression much like how you can express an "if" with the ternary =
operator. However, the specifics of your suggestion give me pause.=20

Also, some of my concerns are contradictory to each other which I will =
admit in advance.

1. I am a strong believer in language design that facilitates =
refactoring. But your syntax would make refactoring from an existing =
switch harder than it would need to be if the syntax more closely =
matched the existing switch. =20

In your proposal you replace colons (:) with fat arrows (=3D>) which has =
no perceptible benefit, at least not for me:

$say =3D switch (date("w")):string {
   case 0 =3D> "weekend!";
   case 1, 2, 3, 4, 5 =3D> "weekday :(";
   case 6 =3D> "weekend!";
};

The same logic in today's PHP:

switch (date("w")) {
   case 0:=20
      $say =3D "weekend!";
      break
   case 1, 2, 3, 4, 5:=20
          $say =3D "weekday :(";
      break
   case 6:     =20
     $say =3D "weekend!";
};

It would be easier to manually refactor if mostly the same syntax was =
used, e.g. with colons (") vs. fat arrows (=3D>):

$say =3D switch (date("w")):string {
   case 0: "weekend!";
   case 1, 2, 3, 4, 5: "weekday :(";
   case 6: "weekend!";
};

So if I had a vote I would vote likely against your RFC with the fat =
arrows but for it if you changed it to use colons instead.

2. However, I find the above more verbose than would be ideal, and I =
would like an optional equivalent of the ternary operator, e.g. both a =
verbose option and a terse option.  I said optional above because =E2=80=94=
 unlike the stated preferences of others here on this list =E2=80=94 I =
celebrate having multiple ways to accomplish the same task because some =
approaches fit a given use-case better than other approaches.

What might a terse option look like? Maybe this, although I might have =
missed conflicts to the existing language:

$say =3D date("w"):string ??? =20
   0: "weekend!";=20
   1, 2, 3, 4, 5: "weekday; :(";=20
   6: "weekend!";
   $default;

I will say, one huge benefit to an inline switch would be allowing for =
switch logic without requiring a `break` (or an explicit `fallthrough`) =
and without any backward compatibility concerns, at least for some =
use-cases.

-Mike




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