What should array() return for const/immutable ElementTypes?

[bearophile]

David Nadlinger:
> Should it always return an array of (head-)mutable elements 
> (since it allocates a copy anyway), or should it preserve 
> constness of the element type?

Ideally the most useful result is a mutable one that is 
implicitly castable to immutable if the mapping function is pure. 
But I don't know if this is always possible.

Bye,
bearophile