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[deadalnix via Digitalmars-d]

On Sunday, 15 November 2015 at 20:11:02 UTC, Dicebot wrote:
> On Sunday, 15 November 2015 at 19:51:09 UTC, Andrei 
> Alexandrescu wrote:
>> Just to clarify - is that referring to the part "We need to 
>> change that if we want things like composable containers that 
>> work with const." or to the "I think it's a good thing to 
>> want" part? -- Andrei
>
> Second part. I don't see a case for const containers at all. 
> Fully immutable functional style ones - sure, I have actually 
> experimented implementing cache this way in 
> https://github.com/Dicebot/mood/blob/master/source/mood/storage/generic_cache.d (thing that powers blog.dicebot.lv). But what would you use const containers for? Mixing mutable and immutable elements in one container? That sounds like a source of much trouble.

For the variance. If you wan't write in the container, you make 
make it so that

ConstContainer<B> implicitly convert to ConstContainer<A> if B 
inherit from A.

You can have code that accept mutable and const container as 
well, which is useful, because you can cram immutable container 
in the ro section.