Question

#include <iostream>
#include <vector>
#include <algorithm> 

using namespace std;

void push_back(int v, vector<int>& coll) 
{
    coll.push_back(v); 
}

int main() 
{
    int a[] = {1, 2, 3, 4, 5};
    std::vector<int> b;
    for_each(a, a + 5, bind2nd(ptr_fun(push_back), b)); 
}

the compiler said:

/usr/include/c++/4.1.2/bits/stl_function.h: In instantiation of ‘std::binder2nd<std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void> >’:
tt5.cpp:15:   instantiated from here
/usr/include/c++/4.1.2/bits/stl_function.h:435: error: forming reference to reference type ‘std::vector<int, std::allocator<int> >&’
/usr/include/c++/4.1.2/bits/stl_function.h: In function ‘std::binder2nd<_Operation> std::bind2nd(const _Operation&, const _Tp&) [with _Operation = std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void>, _Tp = std::vector<int, std::allocator<int> >]’:
tt5.cpp:15:   instantiated from here
/usr/include/c++/4.1.2/bits/stl_function.h:455: error: no matching function for call to ‘std::binder2nd<std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void> >::binder2nd(const std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void>&, std::vector<int, std::allocator<int> >&)’
/usr/include/c++/4.1.2/bits/stl_function.h:429: note: candidates are: std::binder2nd<std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void> >::binder2nd(const std::binder2nd<std::pointer_to_binary_function<int, std::vector<int, std::allocator<int> >&, void> >&)

Answer 1

Your program is perfectly fine, except that you’re using using namespace std; which you should be avoiding. In this case, that is possibly causing the problem.

So I suggest you to remove using namespace std; line, and try using fully-qualified names such as std::vector and std::for_each etc.

Another fix could be this : just don’t use std::for_each, as you don’t need it.

Write this:

int a[] = {1, 2, 3, 4, 5};
std::vector<int> b(a, a+5);

Done!

Now if you want to insert more items later on, then do this:

int *c = get_n_items(n); //get n items 
b.insert(b.end(), c, c+n); //insert all items at end

Hope that helps.

---

Your real scenario:

As you said in the comment:

On my real work,the source collection element is an object.I just want to pick up a member data from each element and insert them to an vector.

If that is the case, then you should std::transform.

Suppose the source is std::vector<person> and you want to pick age member data from each element of this source collection, and insert them into b which is vector<int>:

std::vector<person> persons = get_persons();
std::transform(persons.begin(),        //input begin iterator
               persons.end(),          //input end iterator
               std::back_inserter(b),  //output iterator
               select_age);            //selector  

where select_age is defined as:

int select_age(person const & p) { return p.age; }

If you can use C++11’s lambda, then it is much easier:

std::transform(persons.begin(),        //input begin iterator
               persons.end(),          //input end iterator
               std::back_inserter(b),  //output iterator
               [](person const & p) {return p.age;});  //selector