[Boost-users] Boost.Lambda - using member functions

From: Daniel Dilts (diltsman_at_[hidden])
Date: 2007-08-04 23:26:15

I'm trying to figure out how to use the boost.lambda library, and I'm having
some issues, probably stupid ones, but still, issues. In the following code
I want to remove all obects from m_devices that only have 1 remaining
reference (unique() returns true). Yes, I know that this would be pretty
easy, using regular function pointers, and the like, however, I'm trying to
learn this library.

What am I doing wrong? I would also appreciate any pointers for using
boost.lambda

Whenever I compile the following code on VS2005 I get the following errors:

Warning 1 warning C4512: 'boost::lambda::identity<T>' : assignment operator
could not be generated c:\program files
(x86)\boost\boost_1_34_0\boost\lambda\detail\lambda_functor_base.hpp 43
Warning 2 warning C4512: 'boost::lambda::lambda_functor<T>' : assignment
operator could not be generated c:\program files
(x86)\boost\boost_1_34_0\boost\lambda\detail\lambda_functors.hpp 204
Warning 3 warning C4512: 'boost::lambda::identity<T>' : assignment operator
could not be generated c:\program files
(x86)\boost\boost_1_34_0\boost\lambda\detail\lambda_functor_base.hpp 43
Warning 4 warning C4512: 'boost::lambda::lambda_functor<T>' : assignment
operator could not be generated c:\program files
(x86)\boost\boost_1_34_0\boost\lambda\detail\lambda_functors.hpp 204
Error 5 error C2451: conditional expression of type
'boost::lambda::detail::member_pointer_caller<RET,A,B>' is
illegal c:\program files (x86)\microsoft visual studio
8\vc\include\algorithm 87
Error 6 error C2675: unary '!' :
'boost::lambda::detail::member_pointer_caller<RET,A,B>' does not define this
operator or a conversion to a type acceptable to the predefined
operator c:\program files (x86)\microsoft visual studio
8\vc\include\algorithm 1240
Error 7 error C2582: 'operator =' function is unavailable in
'std::pair<_Ty1,_Ty2>' c:\program files (x86)\microsoft visual studio
8\vc\include\algorithm 1241

My code for the class I'm having trouble with follows:

#pragma once

#include <string>

#include <map>

#include <boost/shared_ptr.hpp>

#include "SocketDevice.h"

namespace Socket

{

class SocketFactory

{

public:

SocketFactory(std::string Host, std::string Port);

virtual ~SocketFactory(void);

protected:

std::pair<std::string, std::string> m_dest;

boost::shared_ptr<SocketDevice> m_device;

static std::map<std::pair<std::string, std::string>,
boost::shared_ptr<SocketDevice>> m_devices;

private:

void RemoveUnreferencedSockets(void);

};

};

#include "SocketFactory.h"

#include <boost/lambda/lambda.hpp>

#include <boost/bind.hpp>

Socket::SocketFactory::~SocketFactory(void)

{

}

void Socket::SocketFactory::RemoveUnreferencedSockets(void)

{

std::remove_if(Socket::SocketFactory::m_devices.begin(),

Socket::SocketFactory::m_devices.end(),

boost::lambda::_1 ->* &std::pair<std::pair<std::string, std::string>,
boost::shared_ptr<SocketDevice> >::second

->* &boost::shared_ptr<SocketDevice>::unique);

}