Re: [Boost-users] [Function] Comparing function objects with std::find

From: Christian Larsen (contact_at_[hidden])
Date: 2008-08-18 13:26:27

Hah, what a coincidence. I see that Hajo Kirchhoff has just asked 
basically the same question two hours before me.

See "[Boost-users] [function] function_equal or function::operator== 
ambiguous overload?"

Is this something which has changed in 1.36.0? Will go check with an 
older version...

Best regards,
Christian

Christian Larsen skrev:
> Hi,
> 
> I'm storing function objects in a std::vector, but to remove one again,
> I need to find an iterator to the one I want to remove. I do this in an
> "unregister" function taking a single boost::function<void ()> as
> parameter. Inside the function I would like to use the std::find
> algorithm to get an iterator to that function in the vector. I'm getting
> compile errors, though; see the example below. How do I fix these?
> 
> I'm using MSVC++ 8 (SP1), and Boost 1.33.1 (can not upgrade).
> 
> Example, where in my "unregister" function I use find as in the last
> part of this example (i.e. I have a Listener and not a plain function
> pointer). This does not compile:
> 
> 
>      #include <algorithm>
>      #include <vector>
>      #include <boost/function.hpp>
> 
>      using namespace std;
>      using namespace boost;
> 
>      void listenerA() {}
>      void listenerB() {}
> 
>      int main()
>      {
>          typedef function<void ()> Listener;
>          typedef vector<Listener> ListenerVector;
> 
>          ListenerVector listeners;
> 
>          listeners.push_back(&listenerA);
>          listeners.push_back(&listenerB);
> 
>          ListenerVector::iterator iter;
> 
>          // This compiles and works
>          iter = find(
>              listeners.begin(), listeners.end(),
>              &listenerB);
> 
>          assert(iter != listeners.end());
> 
>          // This gives:
>          // error C2666: 'boost::operator ==' : 4 overloads have
>          //     similar conversions
>          iter = find(
>              listeners.begin(), listeners.end(),
>              Listener(&listenerB));
> 
>          assert(iter != listeners.end());
> 
>          return 0;
>      }
[SNIP]