c++ - Boost bind with asio::placeholders::error -

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why doesn't work?

--- boost_bind.cc ---

#include <asio.hpp> #include <boost/bind.hpp> #include <boost/function.hpp>  void func1 (const int& i) { }  void func2 (const ::asio::error_code& e) { }  int main () {     ::boost::function<void()> f1 = ::boost::bind (&func1, 1);      // doesn't work!     ::boost::function<void()> f2 = ::boost::bind (&func2, ::asio::placeholders::error);      return 0; }

this error:

 while_true@localhost:~> g++ -lpthread boost_bind.cc -o boost_bind in file included boost_bind.cc:2: /usr/include/boost/bind.hpp: in member function ‘void boost::_bi::list1::operator()(boost::_bi::type, f&, a&, int) [with f = void (*)(const asio::error_code&), = boost::_bi::list0, a1 = boost::arg (*)()]’: /usr/include/boost/bind/bind_template.hpp:20:   instantiated ‘typename boost::_bi::result_traits::type boost::_bi::bind_t::operator()() [with r = void, f = void (*)(const asio::error_code&), l = boost::_bi::list1 (*)()>]’ /usr/include/boost/function/function_template.hpp:152:   instantiated ‘static void boost::detail::function::void_function_obj_invoker0::invoke(boost::detail::function::function_buffer&) [with functionobj = boost::_bi::bind_t (*)()> >, r = void]’ /usr/include/boost/function/function_template.hpp:904:   instantiated ‘void boost::function0::assign_to(functor) [with functor = boost::_bi::bind_t (*)()> >, r = void]’ /usr/include/boost/function/function_template.hpp:720:   instantiated ‘boost::function0::function0(functor, typename boost::enable_if_c::type) [with functor = boost::_bi::bind_t (*)()> >, r = void]’ /usr/include/boost/function/function_template.hpp:1040:   instantiated ‘boost::function::function(functor, typename boost::enable_if_c::type) [with functor = boost::_bi::bind_t (*)()> >, r = void]’ boost_bind.cc:14:   instantiated here /usr/include/boost/bind.hpp:232: error: no match ‘operator[]’ in ‘a[boost::_bi::storage1 (*)()>::a1_ [with int = 1]]’ while_true@localhost:~>

i think should write boost::asio::placeholders::error instead of ::asio::placeholders::error. also, don't understand purpose of :: have in front of boost namespace.


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