[1,2,3].map(function( element){
    return element * 2;
}) //=> [2,4,6]

class Functor
{
    public:
        Functor(int _n) : n(_n) {};
        int operator()() { return n + 3; };
    private:
        int n;
};

template <class T, int N> template <class functorT>
void Vektor<T, N>::callback(functorT func, int i)
{
    entries[i] = func();
}

interface Operator<T> {
  public T apply(T item);
}

/* eine konkrete operation davon */
class AddTwo implements Operator<Integer> {
  public Integer apply(Integer item) {
    return item + 2;
  }
}

class Vektor<A> {

  //...
  
  public void map(Operator<A> operator) {
    for(int i = 0; i < this.length(); i++) {
      
      // apply operator
      A tmp = operator.apply( this.get(i) );
      this.set(i, tmp)

  }

  //..

}

struct myfunctor {
  int operator()(int x) { return x * x; }
};

QLinkedList<QString> list;
...
QString str;
foreach (str, list) {
	qDebug() << str;
}

std::vector::vector<std::string> list;
...
for(const str& item : list) {
	//wasweißich
}