Hi newsgroup!

I am in trouble storing boost function-pointers for=20
object-member-functions in a std:list

defining in Input.h
typedef boost::function2< void, INPUT_EVENT, int> PInputHandler;
std::list<PInputHandler> m_listHandler;

void CInput::RegisterTarget( PInputHandler pHandler )
{
 m_listHandler.push_back(pHandler);
}

using in an instance of CCtrlButton
g_input.RegisterTarget(boost::bind( &CCtrlButton::HandleInputEvents,=20
this, _1, _2 ) );


All works fine until i want to remove a pointer from the list:

void CInput::ReleaseTarget( PInputHandler pHandler )
{
     m_listHandler.remove(pHandler);
}

MSVC6 gives the following Error in the definition of std::list::remove

D:\Programme\Microsoft Visual Studio\VC98\INCLUDE\list(280) : error=20
C2451: Bedingter Ausdruck des Typs 'void' nicht zulaessig
         Ausdruck vom Typ void kann nicht in andere Typen konvertiert wer=
den
         D:\Programme\Microsoft Visual Studio\VC98\INCLUDE\list(278) :=20
Bei der Kompilierung der Member-Funktion 'void __thiscall=20
std::list<class boost::function2<void,enum INPUT_EVENT,int,int>,class=20
std::allocator<class boost::function2<void,enum INP
UT_EVENT,int,int> > >::remove(const class boost::function2<void,enum=20
INPUT_EVENT,int,int> &)' der Klassenvorlage

excuse me that it is in german language, i try to translate it:
"Conditional expression of type 'void' is not valid. Expression of type=20
void cannot be cast into other types"



here is the definition of std::list::remove

void remove(const _Ty& _V)
     {iterator _L =3D end();
     for (iterator _F =3D begin(); _F !=3D _L; )
         if (*_F =3D=3D _V)
             erase(_F++);
         else
             ++_F; }

Something i missed?
I think its the comparison of the to handler-objects that did notwok.

Thanks in advance,
Andr=E9

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It is not possible to compare two Boost.Function objects (because it
can't be implemented "well"). However, recent versions of
Boost.Function can be compared against any type that they can store.
For instance:

function<int(int, int)> f;
function<int(int, int)> g;
if (f == g) ; // ERROR! cannot do this
f = std::plus<int>();
assert(f == std::plus<int>()); // OK

This is enough functionality to implement a template variation of your
ReleaseTarget function, like this:

template<typename Handler>
void ReleaseTarget( const Handler& pHandler )
{
// Can't use remove(), unfortunately, because pHandler would get
converted.
std::list<PInputHandler>::iterator i = m_listHandler.begin();
while (i != m_listHandler.end()) {
    if (*i == pHandler) i = m_listHandler.erase(i);
else ++i;
    }
}

    Doug Gregor

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