如果我定义了const int n、const aClass c、const aStruct s,那么为什么const_cast可以作用于c和s,但是却不能作用于n呢?
如下列代码举的例子:
class C {
public:
int cval;
C(int c) :cval(c){ }
};
struct S {
int sval;
};
int main() {
const int n = 6666;
const C c(666);
const S s{ 66 };
cout << "int, class and structure variables begin with:\n";
cout << "n, c.cval, s.sval = " << n << ", " << c.cval << ", " << s.sval << endl;
// const_cast 用于指针
int *n2 = const_cast<int*>(&n);
C *c2 = const_cast<C*>(&c);
S *s2 = const_cast<S*>(&s);
// const_cast 用于引用
int &n3 = const_cast<int&>(n);
C &c3 = const_cast<C&>(c);
S &s3 = const_cast<S&>(s);
*n2 = 2000;
c2->cval = 200;
s2->sval = 20;
cout << "\nafter const_cast on pointers:\n";
cout << "n, c.cval, s.sval = " << n << ", " << c.cval << ", " << s.sval << endl;
n3 = 3000;
c3.cval = 300;
s3.sval = 30;
cout << "\nafter const_cast on reference:\n";
cout << "n, c.cval, s.sval = " << n << ", " << c.cval << ", " << s.sval << endl;
return 0;
}
运行结果: