Container templates

[Meta]

On Wednesday, 19 February 2014 at 19:44:12 UTC, Meta wrote:
> On Wednesday, 19 February 2014 at 19:10:44 UTC, Frustrated 
> wrote:
>> Are there container templates that one can mixin to classes 
>> that
>> give them container behavior?
>>
>> e.g.,
>>
>> instead of
>>
>> class A
>> {
>>     Array!int x;
>> }
>>
>> I want
>>
>> class A
>> {
>>    mixin Array!int;
>> }
>>
>> so that I can do something like a.Add(3) instead of a.x.Add(3).
>
> One solution is to use alias this.
>
> class A
> {
>     Array!int x;
>     alias x this;
> }
>
> Then you can do a.Add(3) and the method call will be 
> "rewritten" (I don't know if it's *actually* rewritten) as 
> a.x.Add(3).
>
>>myints nor myfloats need to be actual elements of the class. In
>>fact, in this case it might be ok to override them, e.g.,
>>a.add(1) and a.add(5f) above.
>
> This throws a wrench into the above solution, as you can 
> currently only have 1 alias this. However, your idea of inner 
> classes would work, I think.

I played around with it a bit at work and this is a workable 
solution:

import std.container;

class A
{
	this()
	{
		myints = new MyInts();
		myfloats = new MyFloats();
	}
	
	MyInts myints;
	MyFloats myfloats;
	
	private static
	{
		class MyInts
		{
			Array!int x;
			alias x this;
		}
		
		class MyFloats
		{
			Array!float x;
			alias x this;
		}
	}
}

void main()
{
	auto a = new A();
	a.myints.insert(3);
	a.myfloats.insert(3);
}