1//
2// arg_copy_test.cpp - copying a custom placeholder _1 to arg<1>
3//
4// Copyright 2016 Peter Dimov
5//
6// Distributed under the Boost Software License, Version 1.0.
7// See accompanying file LICENSE_1_0.txt or copy at
8// http://www.boost.org/LICENSE_1_0.txt
9//
10
11#include <boost/is_placeholder.hpp>
12#include <boost/bind/arg.hpp>
13
14//
15
16template<int I> struct ph
17{
18};
19
20namespace boost
21{
22
23template<int I> struct is_placeholder< ::ph<I> >
24{
25 enum _vt { value = I };
26};
27
28} // namespace boost
29
30int main()
31{
32 boost::arg<1> a1 = ph<1>();
33 (void)a1;
34}
35

source code of boost/libs/bind/test/arg_copy_test.cpp