"Douglas Gregor" <gregod@cs.rpi.edu> wrote in message news:<200405071039.24725.gregod@cs.rpi.edu>...
On Friday 07 May 2004 10:30 am, Dill, John wrote:
I see your point. But, what if instead of argument_traits being pass by value, it by default passes by T const&? What could be done is to have the bind_t arguments be passed by const reference, and then use reference_wrapper to do type-selection to pass by reference. It still supports literals, and passes by T const& when it can, but everything that is passed by reference must have a ref( object ). The compiler would fail if you try to pass a reference without a reference_wrapper because it by default tries to pass a T const&. This wouldn't require the 2^N overloads but would require you to do a ref( object ) for everything passed by reference. This might also be a workaround for those compilers that don't support T& and T const& overloading.
So we'd be trading lvalue support for literal support. In my experience, lvalues are _much_ more important than literals[*], and we've had these semantics for a really long time (they'll be part of the C++ Library TR), so it will take a truly killer argument to change this.
[*] Thinking of my own work, where I use lots of bind expressions, I remember only once having to name a temporary to get around the T& issue with bind, but can thinking of at least 4 places where I pass lvalues through bind.
Okay, just trying an idea out. Thanks for your comments. John