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Date: Thu, 17 Dec 2020 17:39:37 +0100
Cc: someniatko <someniatko@gmail.com>,
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 Larry Garfield <larry@garfieldtech.com>,
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To: Sara Golemon <pollita@php.net>
Subject: Re: [PHP-DEV] [RFC] Short-match
From: claude.pache@gmail.com (Claude Pache)



> Le 17 d=C3=A9c. 2020 =C3=A0 17:23, Sara Golemon <pollita@php.net> a =
=C3=A9crit :
>=20
> On Wed, Dec 16, 2020 at 6:50 PM someniatko <someniatko@gmail.com> =
wrote:
>>=20
>> `match` is an expression, where as if-else construction is not. This
>> allows for combining it with a potential future feature of single =
line
>> functions and methods. For example (hypothetical syntax is used):
>>=20
>> ```
>> $getNumber =3D fn(int $number) =3D> match {
>>    $number < 0 =3D> NumberKind::NEGATIVE,
>>    $number =3D=3D 0 =3D> NumberKind::ZERO,
>>    $number > 0 =3D> NumberKind::POSITIVE,
>> };
>> ```
>>=20
>=20
> That does read attractively, yes.  This is the example that should =
have
> been offered first as it shows the expression nature shining.
>=20
> To contrast that with what would be possible now in an expressive
> functional form:
>=20
> $getNumber =3D fn(int $number) =3D> [
>  -1 =3D> NumberKind::NEGATIVE,
>  0 =3D> NumberKind::ZERO,
>  1 =3D> NumberKind::POSITIVE,
> ][$number <=3D> 0];
>=20
> The match form *certainly* reads more naturally than the spaceship =
indexing
> form even though both take up equal space.
>=20
> -Sara


If you mean a version of `if` that works in expressions, there already =
exists a standard operator for that. Once its historical associativity =
goof is definitely fixed, you will be able to write:

```
$getNumberKind =3D fn(int $number) =3D>
       $number > 0 ? NumberKind::POSITIVE :
       $number =3D=3D 0 ? NumberKind::ZERO :
       $number < 0 ? NumberKind::NEGATIVE :
       throw new \TypeError;
```

There is a semantic advantage of `match` over `? : `, though, namely its =
exhaustivity: You don=E2=80=99t need to add a =E2=80=9Cpanic=E2=80=9D =
default case in order to catch logic errors.

=E2=80=94Claude=