C++ Bitset 中的 none()函数

bool none();

#include <iostream>
#include <bitset>
using namespace std;
int main()
{
bitset<16> foo;
bitset<4> b(string("1010")); 
if (foo.none())
cout<< foo << " has no bits set.\n";
else
cout<< foo << " has " <<foo.count() << " bits set.\n";
if (b.none())
cout<< b << " has no bits set.\n";
else
cout<< b << " has " <<b.count() << " bits set.\n";
return 0;
}