Hi Jochen,
----- Mail original -----
> De: "Jochen Theodorou" <[email protected]>
> À: "dev" <[email protected]>
> Envoyé: Vendredi 2 Mars 2018 00:57:16
> Objet: Re: [GEP] Switch expressions syntax from Java 11 or 12 (perhaps)
> On 01.03.2018 16:39, Jesper Steen Møller wrote:
> [...]
>> |int numLetters = switch (day) { case MONDAY, FRIDAY, SUNDAY -> 6; case
>> TUESDAY -> 7; case THURSDAY, SATURDAY -> 8; case WEDNESDAY -> 9; };|
>>
>> with
>>
>> |case LABEL -> expression;|
>>
>> essentially sugar for
>>
>> |case LABEL: break expression;|
>
> to make this straight.
>
>> int result = switch (s) {
>> case "Foo":
>> break 1;
>> case "Bar":
>> break 2;
>> default:
>> System.out.println("Neither Foo nor Bar, hmmm...");
>> break 3;
>> }
>
> is the long form of
>
>> int result = switch (s) {
>> case "Foo" -> 1;
>> case "Bar" -> 2;
>> default:
>> System.out.println("Neither Foo nor Bar, hmmm...");
>> break 3;
>> }
>
> The default here has no shorter version, because they are using a
> statement and need to return something in the expression. I understood
> the proposal, that both forms are valid and can be mixed.
>
> There is a few things I dislike...and most of all it is the break
> command here.
>
>> int accumulator = 0
>> LOOP: for (T element : someList) {
>> accumulator += switch (element.type) {
>> case PLUS_ONE -> +1;
>> case MINUS_ONE -> -1;
>> case ERROR:
>> break LOOP;
>> case default -> 0
>> }
>> }
>
> with the idea that element.type is an enum... But my problem is with
> break LOOP. Is LOOP the label LOOP, or is it a constant/variable?
this will not compile, because you can not use return or break/continue inside
an expression switch.
>
> If they need the break only to break out of the switch, then why not
> capitalize on lambdas ?
it was the first idea :)
but lambda can capture effectively final local variable, when a case in an
expression switch acts more like a routine so you can access any variables with
no restriction. So re-using the same syntax for two different semantics is not
a good idea.
The idea is that the expression switch should be used when it's a simple switch
and the C switch with all it's subtle behaviors if the control flow is more
complex,
exactly like you use for(:) if it's a simple loop and for(;;) if it's a more
complex one.
[...]
>
> bye Jochen
cheers,
Rémi
