How to implement an easy_bind() that automagically inserts implied placeholders?

Question

I recently found this nifty snippet on the web - it allows you to bind without having to pass in explicit placeholders:

template 

        

Answer 1

With the indices trick and the ability to tell std::bind about your own placeholder types, here's what I came up with:

#include 
#include 
#include 

template struct placeholder{};

namespace std{
template
struct is_placeholder< ::placeholder> : std::integral_constant{};
} // std::

namespace detail{
template
auto easy_bind(indices, F const& f, Args&&... args)
  -> decltype(std::bind(f, std::forward(args)..., placeholder{}...))
{
    return std::bind(f, std::forward(args)..., placeholder{}...);
}
} // detail::

template
auto easy_bind(std::function const& f, Args&&... args)
    -> decltype(detail::easy_bind(build_indices{}, f, std::forward(args)...))
{
    return detail::easy_bind(build_indices{}, f, std::forward(args)...);
}

Live example.

Take note that I require the function argument to easy_bind to be either of type std::function, or convertible to it, so that I have a definite signature available.