[boost] Feature request: variant::view

Hi, Sometimes we need to view a value as a variant and we don't want to copy the value into a variant. It'd be great if there's a variant::view that works like a variant but holds a reference to the value instead. The constructor should allow any reference to the types as in the variant, and a constructor that takes a reference to the variant, e.g. template class variant::view { view(T1&); view(T2&); ... view(variant&); }; And we can use apply_visitor/get on a view as on a variant. Thoughts? Thanks.