RE: [boost] Re: Proposal --- A type-safe union

From: Yitzhak Sapir (yitzhaks_at_[hidden])
Date: 2002-06-13 06:09:41

> -----Original Message-----
> From: Douglas Gregor [mailto:gregod_at_[hidden]]
>   1) Storage
>     This policy basically collapses in on itself, because 
> there are only two 
> options to choose from, and everyone seems to agree that stack-based 
> allocation is highly preferable. Plus, there are easy ways to 
> simulate heap 
> allocation using stack allocation (Andrei suggests putting a 
> smart_ptr in the 
> variant, and I suggest an 'incomplete' designator, both of 
> which are more 
> fine-grained and more obvious than writing a new policy).

I would still like to have a boost::any type class for limited infinite ranges of types.  Using a smart_ptr<Class> does indeed model some sort of "any class that inherits from some base class".  But I had built an "any iterator to some-predefined-T" type class, based on the way boost::any was implemented.  How would you implement "any iterator to int" using a stack-based variant?  Or the possibility of "any instantiation of template class T" (I am not sure I know if this is useful, though.  The "any iterator" concept is something more specific that seems to be useful in several places that I've written, and which I later saw on the Wiki web page at one point.)