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Date: Tue, 18 Jul 2023 14:57:19 +0200
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To: Larry Garfield <larry@garfieldtech.com>
Cc: Karoly Negyesi <karoly@negyesi.net>, php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] pipes, scalar objects and on?
From: olleharstedt@gmail.com (=?UTF-8?Q?Olle_H=C3=A4rstedt?=)

2023-07-17 21:57 GMT+02:00, Larry Garfield <larry@garfieldtech.com>:
> On Mon, Jul 17, 2023, at 7:07 PM, Olle H=C3=A4rstedt wrote:
>> 2023-07-17 18:58 GMT+02:00, Larry Garfield <larry@garfieldtech.com>:
>>> On Mon, Jul 17, 2023, at 2:57 PM, Olle H=C3=A4rstedt wrote:
>>>> 2023-07-17 14:25 GMT+02:00, Karoly Negyesi <karoly@negyesi.net>:
>>>>> Hi,
>>>>>
>>>>> I tried to read on why the pipe RFC failed but by and large I also
>>>>> failed.
>>>>>
>>>>> The discussion on https://github.com/php/php-src/pull/7214 is very
>>>>> short.
>>>>>
>>>>> https://externals.io/message/114770 is not so short but it seems not
>>>>> to
>>>>> cover the latest version which uses first class functions?
>>>>>
>>>>> Could someone please give me a summary why it failed? I really would
>>>>> like
>>>>> to see it succeed :) I am writing code if not daily but certainly
>>>>> weekly
>>>>> that certainly looks like a pipeline.
>>>>
>>>> The pipe RFC was kinda forced in before a deadline, no?
>>>>
>>>> My own two cents:
>>>>
>>>> * It's trivial to implement a pipe() function or a Pipe class
>>>> * A Pipe class is better than both a function and built-in operator,
>>>> since it can be configured with custom behaviour, e.g. stop or throw
>>>> on empty payload, or repeat on a collection, or even with parallelism
>>>> or concurrency
>>>> * If I had voting rights, I'd vote in favor in a pipe operator :)
>>>
>>> From my recollection, there were a couple of things involved.
>>>
>>> 1. It was intended to pair with the PFA RFC, which didn't pass, which
>>> made
>>> it a bit less compelling.
>>> 2. It was close to the RFC deadline, and it seems people get squeamish
>>> around that.
>>> 3. Some folks wanted Hack-style pipes instead of the pipes used by ever=
y
>>> other language with pipes. I've written before on why that's a worse
>>> design.
>>> 4. Arguments that it can be done in user space, which is not true, as I
>>> have
>>> a user-space implementation and it's comparatively cumbersome and
>>> definitely
>>> slower than a native operator would be.
>>> 5. General "meh" attitude on FP features in general from some people.
>>>
>>> Side note to Olle: If you want a customizable pipe, you've just describ=
ed
>>> a
>>> Monad. :-)  It's literally "contextually-sensitive func concatenation."
>>> A
>>> monadic bind operator would be harder to do with PHP's weaker type
>>> system,
>>> but there are ways it could be done.
>>
>> Mm I don't really agree with that, I think monads make sense only in
>> languages which support them syntactically. A Pipe class is a very
>> straight-forward construction, and the blog posts I've read about
>> monads in PHP don't look pretty at all; lots of syntactic noise going
>> on. But that's another discussion... :)
>
> At its most basic:
>
> class Foo {
>   public function __construct(public readonly mixed $val) {}
>
>   public __bind(callable $c) {
>     return $c($this->val);
>   }
> }
>
> new Foo('beep') >>=3D func(...);
>
> Where >>=3D is the operator that translates to "Call __bind() on the LHS
> object with the callable on the RHS."  Poof, we now have a monad operator=
.
> This one is effectively the same as |> as it doesn't do anything, but you
> can do whatever you want in the __bind() method.

1. You also want syntactic sugar around this to "flatten" monadic
usage; in OCaml it's `let*`.

2. This way you won't get read-process-write pipelines as first-class
values, which you can do if you just make a Pipe class instead. I
think. Correct me if I'm wrong. :)

Olle