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Date: Mon, 11 Jul 2016 16:28:04 +0100
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Subject: Re: [PHP-DEV] Cascade Operator (was Re: [PHP-DEV] Proposal for php7
 class method return)
From: rowan.collins@gmail.com (Rowan Collins)

On 11/07/2016 16:15, Michael Morris wrote:
> But for that to currently work setSomething must return $this.  A cascade
> operator would avoid this.  What about =>  ?
>
> $a->setSomething('here')=>setSomethingElse('there');

This will be ambiguous with array syntax, e.g.

$foo = [ $a->foo() => bar() ]

could be a call to $a->foo() for the key and to bar() for the value, or 
just a chain ending with the array value $a->bar().

Naming things is hard. Inventing operators is harder. ;)

Also note that it's the *first* call that needs a special operator, in 
order to discard the normal return and substitute the left-hand side, 
otherwise mixed chains become ambiguous and probably horrible to 
implement in the engine:

$foo->bar()->baz()=>bob() // what is $this inside bob() ?



> For this sort of chaining I'd propose, in addition to the cascade operator,
> the chain operator. This would work like the cascade operator except that
> the return of the function is implicitly the first parameter of the next
> argument in the chain. Something like this?
>
> $a->add(1, 2):>subtract(3):>add(4); // return 4.

This exact feature was proposed a couple of months ago by Sara Golemon. 
See https://wiki.php.net/rfc/pipe-operator and the accompanying 
discussion http://marc.info/?t=146196088900001&r=4&w=2

As far as I know, it's not been formally withdrawn, so might be 
resurrected in some for for 7.2. It might be interesting to see a 
cascade operator at the same time, but some of the same concerns that 
came up in that discussion will probably apply to any proposal.

Regards,
-- 
Rowan Collins
[IMSoP]