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Date: Mon, 28 Mar 2016 23:23:15 -0300
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To: Stanislav Malyshev <smalyshev@gmail.com>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] RFC Proposal: Maybe monad and execution time
 polymorphic methods
From: fnmartinez88@gmail.com (Facundo Martinez Correa)

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Hi Stanislav,

Yes, as you are saying, it is no easy task. I believe it would make a nice
feature, though. I don't know it is really necessary to use union types, I
believe that with a class hierarchy would suffice. But maybe there is
something that I'm not looking at right, and the unions are needed. It
would certainly need some kind of generics or templates, though I don't
know how powerfull they ought to be. In fact, having generics was something
that also came into my mind when dealing with this project, since I would
use the Builder Patter for my Entities, had a couple of Entities that
extended one from the other and I couldn't play it nice with the Type
Hinting.

Maybe is as Jakub told me, and PHP is not aiming to be Java nor anything
similar in anyway. But I believe that if it is moving into type checking,
it means that the community is seeing it as something needed. So it would
be interesting maybe to have something similar to TypeScript, something
like Gradual Typing. But to have that, everything from both worlds must
work.

Thanks for the reply.
Kind regards,
Facundo

On Mon, Mar 28, 2016 at 9:13 PM, Stanislav Malyshev <smalyshev@gmail.com>
wrote:

> Hi!
>
> > maybe PHP can. Maybe PHP will give me the polymorphism at execution time
> to
> > discern an empty Maybe from the one that is not. So I don't have to check
>
> In order for that to work, we should have a facility to:
> a) define union types
> b) ensure somehow that code dealing with the union type covers all variants
> c) if we really want to be able to handle such types smoothly, we need
> something like monads to be able to convert f(SomeClass $x) to f(Maybe $x).
>
> This does not sound trivial at all. (c) is not strictly required for the
> rest to work, but will also require some kind of generics, since Maybe
> should have information about contained type (maybe what? maybe file,
> maybe database connection, maybe pastrami sandwich?). If you give up on
> (c), you still need some facility like case-of for (b).
>
> And, of course, you will still need to write code to cover the "nothing"
> case of the Maybe. So it might be easier getting a code analyzer that
> would just identify missing null checks?
>
> --
> Stas Malyshev
> smalyshev@gmail.com
>

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