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To: Levi Morrison <levim@php.net>
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Date: Fri, 20 Jan 2017 11:53:19 +0100
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Subject: Re: [PHP-DEV] Pipe Operator v2
From: flaupretre@free.fr (=?UTF-8?Q?Fran=c3=a7ois_Laupretre?=)

Le 19/01/2017 à 22:53, Levi Morrison a écrit :
> On Thu, Jan 19, 2017 at 11:12 AM, François Laupretre <flaupretre@free.fr> wrote:
>> Le 19/01/2017 à 13:54, Levi Morrison a écrit :
>>> The `|>` symbol would be the piping operator with these semantics:
>>>       1. Evaluate the left-hand side.
>>>       2. Evaluate the right-hand side. Assert that the result is callable.
>>>       3. Pass the result from 1. as the single argument to 2.
>>
>> May I suggest extending your 3rd rule to : when the right hand side has the
>> form of a function call, insert the result from 1. as first argument of 2.
>> This way, right hand side may specify additional arguments
> If we only had `|>` this may be good but since we are also proposing
> `$$` then this renders your suggestion unnecessary:
>
>      $string |> trim($$)
>
> Would work just fine with no performance overhead.
>
> Additionally, you could write:
>
>      $input |> array_map($fn, $$)
>
> Or:
>
>      $input |> array_filter($$, $fn)
>
> Basically, `$$` gives the flexibility of passing additional arguments
> and keeps `|>` simple. No need for additional rules for `|>`.

Right, I just suggest to make the '$$' optional when used as first arg 
of a rhs call. Except complex cases like array_xx() functions which will 
generally require an explicit '$$', most cases will feature a '$$' as 
first arg of a function call. This may be considered as better because 
more explicit, but I think the case is prominent enough to justify this 
'shortcut'.

Another question: Will you accept several occurences of '$$' in a RHS ?

Last, a cosmetic suggestion : replace '$$' with '$<' (more explicit as 
'input data', imo).

Regards

François