Ｃ＋＋　　error C2629: unexpected 'class B ('　以找到错误点，但不知原因；

# include <iostream>
# include <string>

using std::endl; using std::cin; using std::cout;
class A{
public:
A(int i):val(i){ cout<<"基类的构造函数"<<endl;  }
virtual ~A(){  cout<<"调用基类的析构"<<endl;};
virtual void get(){  cout<<"val的值："<<val<<endl;  }
protected:
int val;
};

class B:public A{
public:
B(){  cout<<"派生类B的构造函数"<<endl;  }
B(string s,int i):A(i),str(s){  cout<<"派生类B的构造函数"<<endl;  }
~B(){  cout<<"派生类B的析构函数"<<endl;  }
private:
string str;
};

int main(){
B *b=new B("Hello world!!!",99);
cout<<b->get()<<endl;
delete b;
return 0;
}

using std::endl; using std::cin; using std::cout;

修改为

using namespace std；

错误就会消失