Classical Output Iterator

Output iterator allow to write values into a sequence. The classical output iterator is ostream iterator, which is used to write values to the output stream:

#include <iostream>
#include <iterator>
#include <list>

int main (int argc, char * const argv[]) {
    int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
    
    std::copy(&a[0], &a[10], &b[0]);
    
    std::ostream_iterator<int> out(std::cout, " ");
    std::copy(&a[0], &a[10], out);
    
    std::cout << "\n";
    
    return 0;
}

Output iterator allows to write value. For example if first is an output iterator, we can use *first=..., but it is not guarantee that we can obtain the value if will use *first.
More interesting practical use of the output iterators is the STL copy algorithm:

#include <iostream>
#include <iterator>
#include <list>

int main (int argc, char * const argv[]) {
    int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
    int b[10];
    
    std::copy(&a[0], &a[10], &b[0]);
    std::list<int> myList(&a[0], &a[10]);
    
    std::ostream_iterator<int> out(std::cout, " ");
    std::copy(myList.begin(), myList.end(), out);
    std::cout << "\n";
    
    return 0;
}

This program above copies an array a ino array b, then into a list. In the end, the list is copied into the output stream:

Loading program into debugger…

Program loaded.

run

[Switching to process 2192]

Running…

1 2 3 4 5 6 7 8 9 0 

Debugger stopped.

Program exited with status value:0.