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Date: Wed, 4 May 2016 11:47:55 +1000
Message-ID: <CAF1yvASRsmuJwzN-nshEAL=RXDdcqkYF2uBAQxjrmCOZZRhcew@mail.gmail.com>
To: Terry Cullen <terry@terah.com.au>
Cc: Stephen Coakley <me@stephencoakley.com>, internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e01538ac8252d0e0531fa6a10
Subject: Re: [PHP-DEV] [RFC] Pipe Operator
From: me@jesseschalken.com (Jesse Schalken)

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On Tue, May 3, 2016 at 12:53 PM, Terry Cullen <terry@terah.com.au> wrote:

> =E2=80=8BDoesn't Nikic's scalar objects (https://github.com/nikic/scalar_=
objects)
> more or less achieve the same thing while also cleaning up the std lib?
>
> $ret =3D scandir($arg)
>     ->filter(function(){})
>     ->map(function(){})
>     ->merge($someOtherArray);
>


This type of solution is only applicable if the operations to be chained
can be bundled with the definition of the type itself, and are generic
enough that they should be.

Consider the pipe between scandir() and array_filter(...). Suppose I
already have a function or method removeDots(array $paths):array which I
would like to use:

$ret =3D scandir($arg)

    |> $this->removeDots($$)
    |> ...


If the solution is method chaining, then either removeDots() has to be
added to PHP's built-in array type, or scandir() must return a specific
class (eg FileList) which has such a method, instead of a simple array.
Either way, the author of either scandir() or of the "array" type must
predict what operations the user is going to want to chain. That isn't
knowledge they necessarily have, especially since the operations could be
entirely specific to their use case.

With the pipe operator, all three of the left hand side, right hand side
and the type flowing between them can belong to different codebases.

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