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Date: Sat, 23 Jul 2016 15:40:14 +0100
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Subject: Re: [PHP-DEV] Pipe Operator v2
From: rowan.collins@gmail.com (Rowan Collins)

On 23/07/2016 12:15, Rasmus Schultz wrote:
> I mean, maybe it's just me, because I'm familiar with the cascade operator
> from other languages - but it seems simpler, more intuitive, easier to pick
> up, and appears to solve most of the same problems? If so, perhaps it would
> be right to consider the cascade operator as an alternative to this feature.

They're not really the same thing at all; in some ways they're actually 
opposites. The cascade operator is a way of discarding the result of an 
object-oriented expression, and reusing the same context repeatedly. The 
pipe operator is a way of capturing the result of a procedural 
expression, and passing it forward to the next expression.


> It seems to me, the main difference between the pipe operator and a cascade
> operator, is the anonymous context variable $$ created by the pipe operator
> - I think, partially, this is what makes those expression hard to read; the
> context changes (or does it?) along the way, but the (nameless) symbol used
> to reference those objects, in the same expression, are identical.

Yes, the $$ means "result of last expression". In essence, it's a bit 
like Perl's $_ variable, except that it doesn't exist outside the pipe 
syntax. It has to exist to say where you're going to use that result in 
the next expression.

In the cascade operator, you don't need a notation for it, because the 
context is always on the left of the operator:

$foo
     ->>setBar(1) // context is $foo->...
     ->>setBar(2); // context is still $foo->...


But again, this isn't the primary difference between the operators; the 
difference is that one is a way of discarding results, the other is a 
way of carrying results forward.

Regards,

-- 
Rowan Collins
[IMSoP]