#include <string>
#include <iostream>
using namespace std;

void foo(string s = "Hi") {
        s.append("...");
        cout << s << endl;
}

int main() {
        foo();
        foo();
        foo("Yo");
        foo();

        return 0;
}

/*  Assignment on each call (no reusing default values)

Hi...
Hi...
Yo...
Hi...
*/

/* Vs...

>>> def foo(a, L=[]):
...     L.append(a)
...     print L
...
>>> foo(1)
[1]
>>> foo(2)
[1, 2]
>>> foo(3, ['yo'])
['yo', 3]
>>> foo(4)
[1, 2, 4]
>>>

*/