Dill, John wrote:
"Douglas Gregor" <gregod@cs.rpi.edu> wrote in message news:<200405061958.52886.gregod@cs.rpi.edu>...
Ideally, bind(f, _1, _2, _3)(x, y, z) would be exactly equivalent to f(x, y, z). The current bind() implementation gives us nearly this equivalence because it passes by reference, except that we get a failure at compile time if one tries to pass a literal. Going to passing by value would take us further from that ideal equivalence.
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 ).
Technically, bind supports character literals since they are lvalues. It is the rvalues that it has a problem with. Your suggestion is not feasible because in general you do not have control over the call site. As an example, consider std::for_each; it obviously doesn't wrap the argument with ref().