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Date: Sat, 16 Mar 2019 09:12:09 +0000
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Subject: Re: [PHP-DEV] [Proposal] Struct Data Types
From: rowan.collins@gmail.com (Rowan Collins)

On 15 March 2019 15:26:27 GMT+00:00, Nikita Popov <nikita=2Eppv@gmail=2Ecom=
> wrote:
>On Fri, Mar 15, 2019 at 4:16 PM Levi Morrison <levim@php=2Enet> wrote:
>
>> Personally, I think pass by-value with copy-on-write semantics like
>> arrays is the sweet spot=2E Mutability is fine if it is localized=2E
>>
>
>If we introduce something like this, I think it is very important that
>it
>does not use the same property access syntax as ordinary objects, which
>are
>not copy-on-write=2E I do not want to be second guessing whether $x->y =
=3D $z
>is going to copy or not=2E

The more I think about this, the less I agree with it=2E

Firstly, copy-on-write is an implementation detail; the actual semantic we=
're talking about is by-value passing and assignment=2E So semantically, $x=
->y =3D $z would just be modifying local variable $x, as normal=2E It's act=
ually doFoo($x) and $x2 =3D $x which cause the copying, and those look the =
same for objects and arrays=2E

Secondly, array syntax would prevent us from having any methods available =
on structs=2E I suppose you could mix $foo['bar'] for property access and $=
foo->doThing() for method calls, but if doThing() was allowed to modify the=
 object, you've lost the visual highlight of "may cause COW"=2E

A pass-by-value struct would basically just be a way to reduce the overhea=
d to both the programmer and the engine of sprinkling a codebase with the w=
ord "clone"=2E

Regards,

--=20
Rowan Collins
[IMSoP]