Function working w/o std:: namespace qualifier

[Ganado]

While I was coding I realized I forgot to put std:: in front of my function name. Does anyone know why this actually compiles?

Why does this compile without having to do std::random_shuffle?

Edit: Changed post to have only minimal code

#include <algorithm>
#include <vector>

int main() {
	std::vector<int> v {1, 2, 3, 4};
	random_shuffle(v.begin(), v.end());
	return 0;
}

[MiiNiPaa]

This is ADL at work. As both parameter are from std namespace compiler looks for that function in std namespace too.

Replace this line with random_shuffle(&v[0], &v[0] + 4); and it will stop working as arguments are pointers and do not have relaton to any namespace.

[Ganado]

Thanks, interesting feature/set of rules.