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Date: Sun, 15 May 2016 16:45:01 +0200
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To: Rasmus Schultz <rasmus@mindplay.dk>, Joe Watkins <pthreads@pthreads.org>
Cc: Marco Perone <m.perone@mvlabs.it>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7bf10b5485c2a30532e28dfe
Subject: Re: [PHP-DEV] Functorial interfaces
From: me@kelunik.com (Niklas Keller)

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2016-05-15 16:21 GMT+02:00 Rasmus Schultz <rasmus@mindplay.dk>:

> > As a downside, you can't implement it in a normal class anymore and just
> use
> > an instance of that class.
>
> I see that as a plus, because, as a you said:
>
> > That's why you call it with the method name of the interface
>
> Your logic is circular - you also said:
>
> > As a downside, you can't implement it in a normal class anymore and just
> use
> > an instance of that class.
>
> So you want it both ways, class and callable.
>
> But if I'm not supposed to invoke it as a callable, why implement it
> as a callable in the first place?
>
> In other words, you can't really have both - it doesn't really work: a
> callable can be treated as a class, but a class can't be treated as
> callable. If I have to treat everything as classes anyhow, why not
> just use classes?
>
> The only advantage seems to be shorter syntax than anonymous class
> declarations - the resulting objects have to be treated the same way
> in practice,


From the RFC:

The anonymous class version:

- must use referencing, or fetch a new Countable object on each iteration,
- is extremely verbose
- must set dependencies in the constructor
- has no support for lexical scope


The functional interface version:

- is sparse
- is easier to reason about
- does not require the use of references
- supports lexical scope
- Functional interface support does not change the definition of an
interface, and only reuse the definition of a Closure.


> e.g. you can't safely treat them as callables. That's
> where the chain falls off for me: you end up with callables, but you
> shouldn't depend on them being callables, so then why make them
> callables in the first place?

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