无法复制到输出迭代器

Question

Helo. Could anyone tell me why can I assign to output operator but cannot perform copy on it? Copy needs OutputIterator as a thrid argument but I have got some weird errors that you can see here : http://cpp.sh/5akdx

#include <iostream>
#include <iterator>
#include <algorithm>

using namespace std;

bool space(const char &c) {
    return c == ' ';
}
bool not_space(const char &c) {
    return !space(c);
}

template<class Out>
void split(const string &str, Out os) {
    typedef string::const_iterator iter;
    iter i = str.begin();
    while (i != str.end()) {

        i = find_if(i, str.end(), not_space);

        iter j = find_if(i, str.end(), space);

        if (i != str.end())
            //*os++ = string(i, j); //THIS WORKS
            copy(i, j, os);  //THIS DOESN'T WORK
        i = j;
    }
}

int main()
{
    string s;
    while (getline(cin, s))
        split(s, ostream_iterator<string>(cout, "\n"));
    return 0;
}

The problem is that this works

*os++ = string(i, j); 

But it does not:

copy(i, j, os); 

Answer 1

*os++ = string(i, j); 

This line creates one string from the two character iterators and writes it to the output iterator.

copy(i, j, os); 

This line attempts to write each character in the iterator range to the output iterator.

This means that while the first line writes a string to the output iterator, the second line attempts to write individual characters. Those two types are not compatible, and in particular the output iterator only accepts strings. That's the problem.