Re: [boost] Newbie question: using count with a container of boost::shared_ptr

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-03-20 07:55:09

From: "beatlebum1967" <beatlebum1967_at_[hidden]>
> Thanks to this group I have figured out how to use boost::bind in 
> conjunction with for_each to call a member function for each pointer 
> in a container. Now I would like to use a similar idiom to sum the 
> value of a member given a container of boost::shared_ptrs e.g.
> 
> class SomeClass
> {
> ..
> long m_Long;
> }
> 
> std::vector<boost::shared_ptr<SomeClass> > LongVec;
> 
> Use std::count to sum the values of SomeClass::m_Long in LongVec.

The latest CVS bind can do this:

#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <vector>
#include <algorithm>
#include <functional>

struct X
{
    int data;
};

int main()
{
    std::vector< boost::shared_ptr<X> > v;
    std::count_if( v.begin(), v.end(),
        boost::bind< bool >
        (
            std::equal_to<int>(), 0,
            boost::bind( &X::data, _1 )
        )
    );
}