Hi Rowan
I'm not sure <foo> is the right syntax for type guards, but it's possible
> we'd want a different syntax for new switch/match functionality anyway.
I've decided to change the syntax to `(: foo)`. It may look weird at frist
but it is able explain why I think this syntax is more appropriate. Because
PHP already uses `:` to specify return type of functions so `(: foo)`
syntax can be seen as a way to specifying return type of expressions. And
it can be put into the same visual category of cast operators.
$a = (int)$b; // filter
$c = (: int)$d; // guard
This syntax choice may not satisfy everyone's taste but at least it is
explainable. So now there's 2 choices `<foo>` and `(: foo)`. And more
choices are welcome from anyone who think type guard should be a new
feature.
For instance, using a placeholder for the value being tested, like $$ (a
> common
> choice in other languages is _, but that's a valid and commonly used
> function name):
About that, I'm working on a different approach which I would like to show
you after I finished the next demo :)
Regards
On Mon, Oct 21, 2019 at 8:52 PM Rowan Tommins <rowan.coll...@gmail.com>
wrote:
> Hi Kosit,
>
> On Sun, 20 Oct 2019 at 16:20, Kosit Supanyo <webdevxp....@gmail.com>
> wrote:
>
> > You can recognize the difference of those by looking for `=>` right? But
> > the parser generator (bison) cannot do that in LR mode (it maybe can in
> GLR
> > mode but I'm sure that would be unacceptable due to performance
> losses/more
> > memory usage). So workarounds have to be used. I did it by simply return
> > different tokens from the lexer base on previous token before `switch`.
> >>
> >>
>
>
> Thanks for clarifying, I thought it might be something like that.
>
>
>
>
> > * Different comparisons applied to the same variable/expression, e.g.
> >> match($user->getScore()) { case <0 => foo(), case >100 => bar(), default
> >> => baz() }
> >
> >
> > I'd thought about that feature too. But since I also introduced type
> guard
> > operator which uses `<` token it would have parser conflicts and simple
> > workarounds cannot apply.
> >
>
>
>
> I'm not sure <foo> is the right syntax for type guards, but it's possible
> we'd want a different syntax for new switch/match functionality anyway. For
> instance, using a placeholder for the value being tested, like $$ (a common
> choice in other languages is _, but that's a valid and commonly used
> function name):
>
> match ( $user->getScore() ) {
> $$ < 0, $$ > 100 => foo(),
> $$ < 10 => bar(),
> default => baz()
> }
>
> You could also allow the placeholder in the opening clause to define the
> same operation for each case:
>
> match ( $user->getScore() < $$ ) {
> 0, default => foo(),
> 10 => bar(),
> 100 => baz()
> }
>
>
> Regards,
> --
> Rowan Tommins
> [IMSoP]
>
