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To: Stas Malyshev <smalyshev@sugarcrm.com>, 
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Subject: Re: [PHP-DEV] Introducing "Array Of" RFC
From: ajf@ajf.me (Andrea Faulds)



On 20/01/14 22:05, Stas Malyshev wrote:
> Hi!
>
>> Please excuse my lack of knowledge, but if I understand this correctly,
>> this is how generics would work ... using arrays, ignore the syntax and
>> details such as child classes, interfaces, etc.:
>>
>>     $fruits = Array<Fruit>; - declare that $fruits is an array that can only
>> contain instances of class Fruit
>>     function eat(Array<Fruit> $apples) - function eat() will only accept
>> arrays that are declared in the same way as $fruits above
>
> There's two ways to understand "will only accept":
>
> 1. There's a class/type which I call ArrayOfFruit for simplicity. eat()
> checks if $apples is instance of ArrayOfFruit. Some magic inside
> ArrayOfFruit ensures ArrayOfFruit always contains only Fruit.
> 2. eat() goes over $apples which is a regular array, and checks if every
> element in it is instanceof Fruit.
>
> First way is essentially templates, second is not. So far I've seen most
> advocacy in this RFC to go towards the second way.
>

Myself, I want 2 now with syntax that will eventually work for 1 too in 
the future. Soft generics. Array could implicitly cast to Array<Fruit> 
so long as all its members are fruit, in future. But for now, it will 
only be 2. This adds an incentive to add generics: better performance by 
not requiring a runtime check when an Array<Fruit> is passed an not an 
Array of Fruit.

-- 
Andrea Faulds
http://ajf.me/