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Date: Mon, 28 Jun 2021 16:36:15 -0500
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Subject: Re: [PHP-DEV] [RFC] Pipe Operator, take 2
From: larry@garfieldtech.com ("Larry Garfield")

On Mon, Jun 28, 2021, at 3:42 PM, Olle H=C3=A4rstedt wrote:
> 2021-06-28 22:12 GMT+02:00, Larry Garfield <larry@garfieldtech.com>:
> > On Mon, Jun 28, 2021, at 3:04 PM, Rowan Tommins wrote:
> >> On 28/06/2021 20:25, Olle H=C3=A4rstedt wrote:
> >> > Usage (ignoring the pesky undefined constant warnings ><):
> >>
> >>
> >> Unfortunately, you can't ignore those warnings; not least because
> >> they're fatal errors in PHP 8, as they frankly should have been in =
PHP 3.
> >>
> >> You can use our current ugly callable syntax (strings and two-eleme=
nt
> >> arrays); you can tackle the complexity of unifying functions with
> >> constants, and methods with properties (as Levi explained in the ot=
her
> >> thread); or you can add a dedicated callable syntax, which the PFA
> >> proposal gets us with bells on.
> >>
> >> Regards,
> >
> > I think that's a pretty good summary.  There's nothing that pipes or=

> > partials do that you couldn't emulate in user-space today (really, s=
ince 5.3
> > is you really wanted to).  The emulation is just butt-ugly and slowe=
r, which
> > is why most people don't do it except in very specific cases or if t=
hey have
> > a user-space library available that makes it slightly less butt-ugly=
.
> >
> > The purpose of PFA and pipes (and short functions, and auto-capture
> > closures, and basically everything else I've been talking about all =
year) is
> > to make those things prettier and as fast as reasonable, which makes=
 using
> > those techniques more natural.  Once you start down that path, thoug=
h,
> > there's really no usable solution before you get down as far as... P=
FA and
> > Pipes in their current form.
> >
> > --Larry Garfield
>=20
> The challenge is to write something that's pretty enough to be
> considered idiomatic. :) The pipe operator in OCaml is defined by one
> line:
>=20
>     let (|>) v f =3D f v
>=20
> It wasn't always part of core, but eventually it was so common, it got=

> included by default. Same could happen with a pipe() function in PHP,
> without the pipe operator, or that the function becomes so common, a
> new keyword is added instead: `pipe`. But it could probably not happen=

> with a Pipe object requiring you to write ->pipe() at every step -
> it's too much ceremony and boilerplate.
>=20
> By the way, that's alternative 5) New keyword `pipe` to make the
> warning about constants shut up in a certain scope. Plus some other
> magic to allow nice chaining. ^^
>=20
> Olle

"Idiomatic PHP" consists primarily of associative arrays, used in ways n=
o sane person would ever use a dictionary, but the code is in a method s=
o it gets called OOP even though it's barely procedural.

That's not an idiom I have any interest in supporting, and have in fact =
made a career out of training people out of. :-)

There are *already* libraries that let you write ->pipe().  The PHP Leag=
ue has one, for instance:=20

https://github.com/thephpleague/pipeline

I've seen others, but they're no less ugly and offer no better migration=
 path into a core syntax.  PHP is just not designed as a user-extensible=
 language.  (cf, "Growing a Language" by Guy Steele, one of the best pre=
sentations ever given: https://www.youtube.com/watch?v=3D_ahvzDzKdB0)

Also of note, the OCaml definition there is almost exactly the same as t=
he current patch; there's a request out I'm working on now to change the=
 implementation to ensure that the LHS is fully evaluated before the RHS=
, but it's interesting to see that OCaml's version does have the out-of-=
order challenge.  (Although in a functional language it's semantically a=
 meaningless difference, by design.)

Overall, I really don't like the idea of special-casing pipes to change =
what symbol table gets looked up.  That's just asking for edge cases to =
bite us later, especially when the root problem isn't with pipes in the =
first place; it's with PHP lacking either a function-reference syntax or=
 PFA (which gives us a function-reference syntax for free).  Fix the rea=
l problem, don't hack around it in what should be a very simple feature.=


--Larry Garfield