On Mon, 24 Mar 2003, Vladimir Prus wrote:
> Say, I have
>
> std::map<std::string, boost::any> values;
>
> Will I be able to write:
>
> any<fast_allocator> a;
> values[10] = a;
>
> ?
> IOW, I don't think your proposal provides any means to convert between 'any'
> with different allocators. And I'm not sure you can easily achieve that....
Sure you can. You just store a copy of the allocator along with the data
you are holding. The holders would look like this:
struct holder_base {
virtual ~holder_base() {};
virtual holder_base* clone() = 0;
virtual void destroy() = 0;
template<typename T, typename Allocator>
struct holder : holder_base
{
holder(const T& value, const Allocator& allocator)
: value(value), allocator(allocator) {}
~holder() {}
virtual holder* clone() = 0
{
holder* result = allocator.allocate(1);
new (result) holder(value, allocator);
return result;
}
virtual void destroy() = 0
{
Allocator allocator(this->allocator);
this->~holder();
allocator.deallocate(this);
}
};
This requires allocators to be CopyConstsructible, of course.
Doug
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