Chris:
4) What about and any_base<> + any_derived<> ? Based on several cases where I've seen/done type deletion a common pattern is to define a base class and a templated derived class. boost::asio::detail::op_base+op
Steven Watanabe:
I don't understand. If you want a base/templated derived class, the easiest thing is just to implement it that way.
I don't want to have to do it. Typically each time someone runs into one of these problems they do their type-deletion that way. Each time it's done for a particular use case, usually based on the signature of a callable concept. If you want more examples of this: asio::detail::descriptor_read_op => descriptor_read_op_base - deletes the handler type descriptor_read_op_base =>reactor_op - deletes the buffer type Could/would you do that more cleanly with an any<>? I think so. If you're OK with heap storage, instead of holding a base* you can hold an any<..>. I'm not so sure if you want control over the storage, though it looks like any<...,_self&> allows me to avoid the heap. There'd have to be an indirection more. I think it can be avoided by your library by exposing something you're forced to implement anyway. Chris