Re: [RFC][DISCUSSION] Match expression v2

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  110675
June 18, 2020 20:51 tovilo.ilija@gmail.com (Ilija Tovilo)
Hi Björn

>> I'd like to announce the match expression v2 RFC: >> https://wiki.php.net/rfc/match_expression_v2
> Well one could argue that when working with legacy code containing > switch statements where one gradually migrates to match, it might be > easier to have the same separator, i.e. ":".
I think that's somewhat of a moot point. The syntax of match is quite different (match instead of switch, no case, no break, colon instead of case, comma instead of semicolon, trailing semicolon). Just making one of those the same doesn't make a meaningful difference for ease of migration.
> Is the proposed => separator inspired by Rust or Scala? Checked what > other languages used and for switch it's ":" of course. So one might > argue that to align with match statements in other languages "=>" is > a good choice, but OTOH if ones sees match as an enhanced switch, > having ":" as a separator is another alternative.
Since nobody else asked for it, just for you I compiled a list of other languages :) https://gist.github.com/iluuu1994/11ac292cf7daca8162798d08db219cd5 The conclusion: Most languages also use some form of arrow. It makes sense to me to stay consistent with those languages. Ilija
  110695
June 22, 2020 15:35 bjorn.x.larsson@telia.com (=?UTF-8?Q?Bj=c3=b6rn_Larsson?=)
Hi Ilija,Den 2020-06-18 kl. 22:51, skrev Ilija Tovilo:

> Hi Björn > >>> I'd like to announce the match expression v2 RFC: >>> https://wiki.php.net/rfc/match_expression_v2 >> Well one could argue that when working with legacy code containing >> switch statements where one gradually migrates to match, it might be >> easier to have the same separator, i.e. ":". > I think that's somewhat of a moot point. The syntax of match is quite > different (match instead of switch, no case, no break, colon instead > of case, comma instead of semicolon, trailing semicolon). Just making > one of those the same doesn't make a meaningful difference for ease of > migration. Agree on that! One thing though. Is semicolon mandatory or is it optional
like in the first RFC? Feels a bit odd with a semicolon after a curly bracket.
>> Is the proposed => separator inspired by Rust or Scala? Checked what >> other languages used and for switch it's ":" of course. So one might >> argue that to align with match statements in other languages "=>" is >> a good choice, but OTOH if ones sees match as an enhanced switch, >> having ":" as a separator is another alternative. > Since nobody else asked for it, just for you I compiled a list of > other languages :) > > https://gist.github.com/iluuu1994/11ac292cf7daca8162798d08db219cd5 > > The conclusion: Most languages also use some form of arrow. It makes > sense to me to stay consistent with those languages. > > Ilija
I think this is a very good motivation on why select => as a symbol and I'm glad it's listed in the RFC. r//Björn
  110697
June 22, 2020 16:05 benas.molis.iml@gmail.com (Benas IML)
On Mon, Jun 22, 2020, 6:35 PM Björn Larsson larsson@telia.com>
wrote:

> Hi Ilija,Den 2020-06-18 kl. 22:51, skrev Ilija Tovilo: > > > Hi Björn > > > >>> I'd like to announce the match expression v2 RFC: > >>> https://wiki.php.net/rfc/match_expression_v2 > >> Well one could argue that when working with legacy code containing > >> switch statements where one gradually migrates to match, it might be > >> easier to have the same separator, i.e. ":". > > I think that's somewhat of a moot point. The syntax of match is quite > > different (match instead of switch, no case, no break, colon instead > > of case, comma instead of semicolon, trailing semicolon). Just making > > one of those the same doesn't make a meaningful difference for ease of > > migration. > Agree on that! One thing though. Is semicolon mandatory or is it optional > like in the first RFC? Feels a bit odd with a semicolon after a curly > bracket. >
It's mandatory since it's an expression, not a block. Another example of an expression would be a closure: ``` $fn = function () { ... }; // a semicolon is mandatory here. ```
>> Is the proposed => separator inspired by Rust or Scala? Checked what > >> other languages used and for switch it's ":" of course. So one might > >> argue that to align with match statements in other languages "=>" is > >> a good choice, but OTOH if ones sees match as an enhanced switch, > >> having ":" as a separator is another alternative. > > Since nobody else asked for it, just for you I compiled a list of > > other languages :) > > > > https://gist.github.com/iluuu1994/11ac292cf7daca8162798d08db219cd5 > > > > The conclusion: Most languages also use some form of arrow. It makes > > sense to me to stay consistent with those languages. > > > > Ilija > > I think this is a very good motivation on why select => as a symbol and > I'm glad it's listed in the RFC. > > r//Björn > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: https://www.php.net/unsub.php > >
  110701
June 23, 2020 08:23 bjorn.x.larsson@telia.com (=?UTF-8?Q?Bj=c3=b6rn_Larsson?=)
Den 2020-06-22 kl. 18:05, skrev Benas IML:

> On Mon, Jun 22, 2020, 6:35 PM Björn Larsson larsson@telia.com> > wrote: > >> Hi Ilija,Den 2020-06-18 kl. 22:51, skrev Ilija Tovilo: >> >>> Hi Björn >>> >>>>> I'd like to announce the match expression v2 RFC: >>>>> https://wiki.php.net/rfc/match_expression_v2 >>>> Well one could argue that when working with legacy code containing >>>> switch statements where one gradually migrates to match, it might be >>>> easier to have the same separator, i.e. ":". >>> I think that's somewhat of a moot point. The syntax of match is quite >>> different (match instead of switch, no case, no break, colon instead >>> of case, comma instead of semicolon, trailing semicolon). Just making >>> one of those the same doesn't make a meaningful difference for ease of >>> migration. >> Agree on that! One thing though. Is semicolon mandatory or is it optional >> like in the first RFC? Feels a bit odd with a semicolon after a curly >> bracket. >> > It's mandatory since it's an expression, not a block. Another example of an > expression would be a closure: > > ``` > $fn = function () { > ... > }; // a semicolon is mandatory here. > ```
Absolutely so. I was thinking of the case mentioned in v1 RFC when it's used as a stand-alone expression. match ($y) { .... };  ` Optional? r//Björn L
  110703
June 23, 2020 08:30 benas.molis.iml@gmail.com (Benas IML)
On Tue, Jun 23, 2020, 11:23 AM Björn Larsson larsson@telia.com>
wrote:

> Den 2020-06-22 kl. 18:05, skrev Benas IML: > > > On Mon, Jun 22, 2020, 6:35 PM Björn Larsson larsson@telia..com> > > wrote: > > > >> Hi Ilija,Den 2020-06-18 kl. 22:51, skrev Ilija Tovilo: > >> > >>> Hi Björn > >>> > >>>>> I'd like to announce the match expression v2 RFC: > >>>>> https://wiki.php.net/rfc/match_expression_v2 > >>>> Well one could argue that when working with legacy code containing > >>>> switch statements where one gradually migrates to match, it might be > >>>> easier to have the same separator, i.e. ":". > >>> I think that's somewhat of a moot point. The syntax of match is quite > >>> different (match instead of switch, no case, no break, colon instead > >>> of case, comma instead of semicolon, trailing semicolon). Just making > >>> one of those the same doesn't make a meaningful difference for ease of > >>> migration. > >> Agree on that! One thing though. Is semicolon mandatory or is it > optional > >> like in the first RFC? Feels a bit odd with a semicolon after a curly > >> bracket. > >> > > It's mandatory since it's an expression, not a block. Another example of > an > > expression would be a closure: > > > > ``` > > $fn = function () { > > ... > > }; // a semicolon is mandatory here. > > ``` > > Absolutely so. I was thinking of the case mentioned in v1 RFC when it's > used > as a stand-alone expression. > match ($y) { > ... > }; > Then it's not a standalone expression but a block. In this case, you cannot
add an optional semicolon at all. But this RFC v2 is not proposing to add a block, therefore you won't be allowed to use `match` construct as a standalone expression anyways. ` Optional?
> > r//Björn L >
  110704
June 23, 2020 08:34 tovilo.ilija@gmail.com (Ilija Tovilo)
Hi Benas

>> I'd like to announce the match expression v2 RFC: >> https://wiki.php.net/rfc/match_expression_v2
> Then it's not a standalone expression but a block. In this case, you cannot add an optional semicolon at all. > > But this RFC v2 is not proposing to add a block, therefore you won't be allowed to use `match` construct as a standalone expression anyways.
Using match as a standalone expression is definitely allowed, just like any other expression. // This is fine, the semicolon is required match ($foo) { $bar => baz(), }; Ilija
  110705
June 23, 2020 08:39 benas.molis.iml@gmail.com (Benas IML)
Hey,

On Tue, Jun 23, 2020, 11:34 AM Ilija Tovilo ilija@gmail.com> wrote:

> Hi Benas > > >> I'd like to announce the match expression v2 RFC: > >> https://wiki.php.net/rfc/match_expression_v2 > > > Then it's not a standalone expression but a block. In this case, you > cannot add an optional semicolon at all. > > > > But this RFC v2 is not proposing to add a block, therefore you won't be > allowed to use `match` construct as a standalone expression anyways. > > Using match as a standalone expression is definitely allowed, just > like any other expression. > > // This is fine, the semicolon is required > match ($foo) { > $bar => baz(), > }; >
Yup but it won't return you out of the function. For example, this wouldn't work: ``` function test(int $value): bool { match($value) { 0 => false, 1 => true } } $test = test(1); ``` But it seems by standalone expressions, Bjorn meant your example. Sorry for the confusion, I thought he was referring to blocks.
> Ilija > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: https://www.php.net/unsub.php > >
  110702
June 23, 2020 08:30 tovilo.ilija@gmail.com (Ilija Tovilo)
Hi Björn

>> I'd like to announce the match expression v2 RFC: >> https://wiki.php.net/rfc/match_expression_v2
> Absolutely so. I was thinking of the case mentioned in v1 RFC when it's used > as a stand-alone expression. > match ($y) { > ... > }; > ` Optional?
In this RFC the semicolon is required. Many people thought the grammar rules for the optional semicolon were confusing which is why I dropped that feature in this RFC. Ilija
  110706
June 23, 2020 08:54 bjorn.x.larsson@telia.com (=?UTF-8?Q?Bj=c3=b6rn_Larsson?=)
Den 2020-06-23 kl. 10:30, skrev Ilija Tovilo:

> Hi Björn > >>> I'd like to announce the match expression v2 RFC: >>> https://wiki.php.net/rfc/match_expression_v2 >> Absolutely so. I was thinking of the case mentioned in v1 RFC when it's used >> as a stand-alone expression. >> match ($y) { >> ... >> }; >> ` Optional? > In this RFC the semicolon is required. Many people thought the grammar > rules for the optional semicolon were confusing which is why I dropped > that feature in this RFC. > > Ilija
Ok, thanks for the clarification. The reason for me to bring this up is that I was pondering on if this is the only place in PHP where a semicolon is required after a curly bracket when not used in an expression. If so I a counter argument could that it it is confusing for programmers, not so privy to all the ins and outs of PHP. Anyway, maybe a feature to consider for a future 8.1 RFC. r//Björn
  110709
June 23, 2020 12:09 rowan.collins@gmail.com (Rowan Tommins)
On Tue, 23 Jun 2020 at 09:54, Björn Larsson larsson@telia.com>
wrote:

> > Ok, thanks for the clarification. The reason for me to bring > this up is that I was pondering on if this is the only place in > PHP where a semicolon is required after a curly bracket > when not used in an expression. >
Two things: - as proposed here, match is *always* an expression; it just happens that PHP lets you throw away the result of an expression, so "match($x){};" is a valid statement for the same reason "42;" is a valid statement - as Ilija mentioned, ending a statement with an anonymous function also leads to the combination "};" function returnsFunc() { return function() { echo "Hello, world!\n"; }; } function returnsMatchResult($x) { return match($x) { 1=> "Hello", 2=>"world" }; } I'd also note that while there aren't currently many cases where it would be ambiguous whether a statement or expression was intended, new ones might be added in future. For instance, post-fix conditionals (like in Perl and Ruby) would give us match($x) { ... } if $condition; This kind of syntax short-cut tends to end up with complex rules of "it's optional except when it's not", which I'm personally not a fan of. Regards, -- Rowan Tommins [IMSoP]