#include <QCoreApplication>
#include <iostream>using namespace std;//包含后就不用 std::cout了，直接coutnamespace ns1 {int pram = 3;void foo(void){std::cout << "ns1 " << std::endl;}}
namespace ns2 {int pram = 6;}
namespace ns2 {void foo(void){std::cout << "ns2 " << std::endl;}}
int main(int argc, char *argv[])
{QCoreApplication a(argc, argv);std::cout << "233" << std::endl;std::cout << "666!" << std::endl;std::cout << ns1::pram << std::endl;std::cout << ns2::pram << std::endl;ns1::foo();ns2::foo();using namespace ns1;//名字空间指令std::cout << pram << std::endl;foo();
//    using namespace ns2;//引发歧义
//    std::cout << pram << std::endl;
//    foo();using ns2::pram;//名字空间声明std::cout << pram <<std::endl;using ns2::foo;//名字空间声明foo();
//    using ns1::foo;//名字空间声明,这里会引起歧义
//    foo();
//    int x,y;
//    std::cin >> x >> y;
//    std::cout << x << '+' << y << " = " << x + y << std::endl;return a.exec();
}