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Date: Mon, 2 May 2016 19:57:40 -0500
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Subject: Re: [PHP-DEV] [RFC] Pipe Operator
From: me@stephencoakley.com (Stephen Coakley)

On 04/30/2016 06:14 PM, Rowan Collins wrote:
> On 29/04/2016 20:58, Sara Golemon wrote:
> Let's say I want to add a condition just before getFileArg(); with the
> current version I've got to:
> - go to the beginning of the chain, and assign to something other than $ret
> - go to where I want to break the chain, and reintroduce the $ret
> assignment
> - add my check in the gap, using the variable I just added at the
> beginning of the chain
>
> $fileList = scandir($arg)
>      |> array_filter($$, function($x) { return $x !== '.' && $x != '..'; })
>      |> array_map(function ($x) use ($arg) { return $arg . '/' . $x; },
> $$);
> if ( someCheck($fileList) {
>      something();
> }
> $ret = getFileArg($$)
>      |> array_merge($ret, $$);
>
> The syntax is fighting me here, making me jump around the code. But if
> assignment was always on the end of the chain, I would only need to make
> changes at the point where I was breaking the chain. The basic pattern
> would be:
>
> |=> $tempVar; // terminate the chain and capture the value
> // do stuff with $tempVar
> $tempVar // restart the chain
>
> So:
>
> scandir($arg)
>      |> array_filter($$, function($x) { return $x !== '.' && $x != '..'; })
>      |> array_map(function ($x) use ($arg) { return $arg . '/' . $x; }, $$)
>      |=> $fileList;
> if ( someCheck($fileList) {
>      something();
> }
> $fileList
>      |> getFileArg($$)
>      |> array_merge($ret, $$)
>      |=> $ret;
>
> If I don't need the condition any more, I can delete lines 4 to 8, and
> I've got back my original chain.

Could you use a closure instead to accomplish this? (Again yes, Sara 
could you clarify if this is permitted?)

$ret = scandir($arg)
         |> array_filter($$, function($x) { return $x !== '.' && $x != 
'..'; })
         |> array_map(function ($x) use ($arg) { return $arg . '/' . $x; 
}, $$)
         |> (function($fileList) {
                if (someCheck($fileList)) {
                    something();
                }
                return $fileList;
            })($$)
         |> getFileArg($$)
         |> array_merge($ret, $$);

Not completely the best, but perhaps there's some sort of an idea here?

-- 
Stephen