Question

How to call class member function using std::for_each
Here is what my class is.

template <typename _TyG>
class Graph {
private:        
public:
    typedef typename Vertex<_TyG>                           VertexType;
    typedef typename std::set<VertexType>                   GraphStorage;
    typedef typename GraphStorage::iterator                 GraphStorageItr;
    typedef typename GraphStorage::const_iterator           GraphStorageConstItr;

    typedef typename std::list<VertexType *>                AdjListType;
    typedef typename AdjListType::iterator                  AdjListTypeItr;
    typedef typename AdjListType::const_iterator            AdjListTypeConstItr;

    typedef typename std::map<  VertexType*, 
                                AdjListType, 
                                CompareIterator<VertexType*> >  GraphType;

    typedef typename GraphType::iterator                    GraphTypeItr;
    typedef typename GraphType::const_iterator              GraphTypeConstItr;

void _init_not_visited(GraphTypeItr inItr) {
}
void DepthFirstSearch() {
        std::for_each(m_Graph.begin(), m_Graph.end(), std::bind2nd(std::mem_fun(&Graph::_init_not_visited),this));
    }
}

What I want is to pass iterator to _init_not_visited. But I am confuse on how to use std::for_each, current code is giving me compilation error.

Answer 1

I do not think you can do what you want to do with std::for_each. As std::for_each calls the given function on each value in the sequence and not each iterator position in the sequence. std::for_each might look like:

template <class iter_t, class fn_t>
fn_t for_each(iter_t first iter_t const last, fn_t fn)
{
    for (; first != last; ++first)
        fn(*first);
    return fn;
}

You can either write your own for_each_iter such as:

template <class iter_t, class fn_t>
fn_t for_each_iter(iter_t first, iter_t const last, fn_t fn)
{
    for (; first != last; ++first) {
        fn(first);
    }

    return fn;
}

Or change _init_not_visited() to take GraphType::value_type instead of GraphTypeItr. Assuming that you can still write the function with that argument.