2011/4/11 Ion Gaztañaga <igaztanaga@gmail.com>
El 11/04/2011 3:22, Jeffrey Lee Hellrung, Jr. escribió:
On Mon, Apr 4, 2011 at 10:36 AM, Jeffrey Lee Hellrung, Jr.< jeffrey.hellrung@gmail.com> wrote: [...snipping original description...]
Sorry for the lack of feedaback! I tried to your example in some compilers and checked that MSVC7.1 does not like pointer to function storage in the generic rv (it's a msvc bug, but annoying, nevertheless).
It sounds like that could be easily worked around without too much obfuscation.
I've been very busy with several interprocess issues and I couldn't take time to study this but I promise to dedicate some time soon.
Great, thanks; as long as I know that you've seen the message, I'm happy :)
I was a bit confused as you use a function object in your example. Can't we take rid of that function object and apply it to free functions?
You can, but you would still need a function object to execute the visitor pattern on the genrv object, since the visitor must be polymorphic (it must accept many different argument types). Making the function object *both* the visitor *and* the "housing" of the overload set is merely a convenience.
How can we apply this to the constructor of an object?
Unfortunately, here the technique can get quite cumbersome. After thinking a little about this, I think you'd have to be in one of the following situations: - Use no initializer lists, and perform the construction in an "init" method. This should be okay for, e.g., pimpl classes. - All member object(s) and base class(es) that receive the to-be-forwarded argument can accept a genrv object. - Use some kind of "typeless opaque storage" for all member object(s) that receive the to-be-forwarded argument to delay initialization until the constructor body. Should be strongly discouraged, but sometimes you gotta do what you gotta do... - Jeff