H>#include <iostream>
H>#include <fstream>

H>using namespace std;

H>void f(ostream* stream,const char* s)
H>{ 
H>    *stream << s; 
H>}

H>int main(int argc, char **argv)
H>{
H>    fstream f("test.txt", ios::app);
H>    string s;
H>    ostringstream out(s);
    
H>    f(static_cast<ostream*>(&f),"test");
H>    f(static_cast<ostream*>(&out), "test");
H>    f(static_cast<ostream*>(&cout), "test");
H>    return 0;
H>}

H>