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Date: Sun, 24 Nov 2024 14:38:17 +0000
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Subject: Re: [PHP-DEV] [RFC] Data Classes
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

Hi Larry,

I think that's a useful breakdown of the concepts involved. I don't 
think it's a bad thing to have a feature that covers multiple of them - 
common cases shouldn't need a long string of modifiers like "immutable 
copyonwrite valueequality class Point { ... }" - but being explicit 
about what we are and are not including is wise.

There is one point I'd like to nitpick on, though:


On 23/11/2024 20:35, Larry Garfield wrote:
> 3. Physical equality.  This is what === does, and checks that two variables refer to the same memory location.  Physical equality implies logical equality, but not vice versa.


PHP's === operator is not, in general, an identity operator; it is a 
"strict equality" operator, whose exact meaning depends on the type of 
its operands.

For "scalar" types, it checks the concrete type and the value: 1+1 === 
2, and strtoupper('hello') === 'HELLO'

For arrays, the definition is applied recursively: two arrays are 
loosely equal if all their elements are loosely equal, and strictly 
equal if all their elements are strictly equal.

Objects are really the outlier, overloading the operator to mean 
"identity" rather than applying a strict value comparison.

Example: https://3v4l.org/udOoU

If we introduce some new "value type", it seems very reasonable to use 
the same recursive definition of strict equality used for arrays.


-- 
Rowan Tommins
[IMSoP]