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Date: Thu, 23 Apr 2020 00:31:52 +0300
Message-ID: <CA+hqhpcMVo=rBGHiokBRqYqHuT1T8SHxi3gg7xjuqbx44m7uSQ@mail.gmail.com>
To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Function pipe operator
From: weirdan@gmail.com (Bruce Weirdan)

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Haskell has & operator in Data.Function module which is exact equivalent of
the proposed feature.
Link:
https://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Function.html#g:2
Example: https://repl.it/repls/KindLightsalmonApplicationserver

On Wed, Apr 22, 2020 at 9:09 PM Larry Garfield <larry@garfieldtech.com>
wrote:

> On Wed, Apr 22, 2020, at 3:25 AM, Guilliam Xavier wrote:
> > On Tue, Apr 21, 2020 at 4:44 PM Larry Garfield <larry@garfieldtech.com>
> wrote:
> > >
> > > On Mon, Apr 20, 2020, at 11:20 PM, Stanislav Malyshev wrote:
> > > > Just a small pedantry note - in a comparison section, the RFC
> compares
> > > > this syntax to function composition. But this is not function
> > > > composition. This is a syntax sugar for calling two functions one
> after
> > > > another, not operator that produces a function. It sounds pedantic
> but
> > > > it's rather important distinction - if |> is composition, than $foo
> |>
> > > > $bar is a new callable provided $foo and $bar are callable (but no
> > > > function is actually being called here!). If |> is call syntax, it's
> > > > actually the result of calling $bar($foo).
> > > >
> > > > So comparing it to function composition is a bit confusing.
> Otherwise it
> > > > looks OK to me, except the syntax for calling functions and methods
> is a
> > > > bit awkward, but it's not the problem of this RFC I imagine.
> > >
> > > I'm not sure I follow.  The only place composition is mentioned is in
> the F# section, where it calls out specifically that we're implementing
> "pipe forward" and *not* the composition operators ( >> ).  Is that unclear?
> >
> > Actually it's also mentioned in the Haskell section, but as "function
> > concatenation" (which adds to the confusion I guess).
>
> Ah, I see what you mean.  I've adjusted that section to be clearer about
> what Haskell does.
>
> > Speaking of Haskell, that reminded me of
> > http://learnyouahaskell.com/a-fistful-of-monads#walk-the-line where
> > the author defines a custom `-:` operator such that `x -: f` desugars
> > to `f x` (equivalent to how `$x |> $f` would desugar to `$f($x)` with
> > the RFC), which allows to write e.g. `xs -: sort -: reverse` instead
> > of `reverse (sort xs)` or `(reverse . sort) xs`.
>
> If I ever actually wrote Haskell, I'd find that extremely useful. :-)
>
> --Larry Garfield
>
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>

-- 
  Best regards,
      Bruce Weirdan                                     mailto:
weirdan@gmail.com

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