public: virtual void quack() {
for (std::vector<Quackable*>::iterator it = quackers.begin(); quackers.end() != it; ++it) {
Quackable* quacker = *it;
quacker->quack();
}
}
void simulate(Quackable& duck){
duck.quack();
}
void quack()
{
duck->quack();
numberOfQuacks++;
}