[C++] static_cast, dynamic_cast, reinterpret_cast, const_cast

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static_cast(exp) function 可以將 exp 轉換成 new_type，但是不能夠確保轉換一定會成功，upcasting 一般可以成功，但是 downcasting 則需要確認是否轉換失敗。

struct B {};
struct D : B {};

int main(){
D d;
B br = d; // upcast via implicit conversion
D another_d = static_cast(br); // downcast
}

const_cast() function 可以將 const 變數的值做修改，new_type 必須要是a pointer, reference, or pointer to member to an object type。

void change(const int* p) {
    int *v = const_cast(p);
    *v = 20;
}

int main(){
    const int* k1 = new int(1000);
    int* k2 = new int(2000);
    *k1 = 100; // Compling error
    *k2 = 200; 
    cout << *k1 << " " << *k2 << endl;
    change(k1);
    change(k2);
    cout << *k1 << " " << *k2 << endl;
}

output of the above codes:

1000 200
20 20

參考連結