functional, bind1st и mem_fun

Question

Почему это не компилируется?

#include <functional> 
#include <boost/function.hpp> 

class A { 
    A() { 
     typedef boost::function<void()> FunctionCall; 
     FunctionCall f = std::bind1st(std::mem_fun(&A::process), this); 
    } 
    void process() {} 
}; 

Ошибка:

In file included from /opt/local/include/gcc44/c++/bits/stl_function.h:712, 
       from /opt/local/include/gcc44/c++/functional:50, 
       from a.cc:1: 
/opt/local/include/gcc44/c++/backward/binders.h: In instantiation of 'std::binder1st<std::mem_fun_t<void, A> >': 
a.cc:7: instantiated from here 
/opt/local/include/gcc44/c++/backward/binders.h:100: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' 
/opt/local/include/gcc44/c++/backward/binders.h:103: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' 
/opt/local/include/gcc44/c++/backward/binders.h:106: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' 
/opt/local/include/gcc44/c++/backward/binders.h:111: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' 
/opt/local/include/gcc44/c++/backward/binders.h:117: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' 
/opt/local/include/gcc44/c++/backward/binders.h: In function 'std::binder1st<_Operation> std::bind1st(const _Operation&, const _Tp&) [with _Operation = std::mem_fun_t<void, A>, _Tp = A*]': 
a.cc:7: instantiated from here 
/opt/local/include/gcc44/c++/backward/binders.h:126: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' 
In file included from /opt/local/include/boost/function/detail/maybe_include.hpp:13, 
       from /opt/local/include/boost/function/detail/function_iterate.hpp:14, 
       from /opt/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:47, 
       from /opt/local/include/boost/function.hpp:64, 
       from a.cc:2: 
/opt/local/include/boost/function/function_template.hpp: In static member function 'static void boost::detail::function::void_function_obj_invoker0<FunctionObj, R>::invoke(boost::detail::function::function_buffer&) [with FunctionObj = std::binder1st<std::mem_fun_t<void, A> >, R = void]': 
/opt/local/include/boost/function/function_template.hpp:913: instantiated from 'void boost::function0<R>::assign_to(Functor) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' 
/opt/local/include/boost/function/function_template.hpp:722: instantiated from 'boost::function0<R>::function0(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' 
/opt/local/include/boost/function/function_template.hpp:1064: instantiated from 'boost::function<R()>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' 
a.cc:7: instantiated from here 
/opt/local/include/boost/function/function_template.hpp:153: error: no match for call to '(std::binder1st<std::mem_fun_t<void, A> >)()' 

Answer 1

Поскольку bind1st требует двоичного объекта функции. Однако вы передаете унарный объект функции. Объектные связующие объекты C++ 03 не такие сложные, как те, которые были найдены в boost или tr1. Фактически, они страдают от основных проблем, таких как неспособность обрабатывать функции со справочными параметрами.

Поскольку вы уже используете импульс, я рекомендую использовать boost::bind

FunctionCall f = boost::bind(&A::process, this); // yay!