[英]Redefining Friend Function of Base Class in Derived Class
我想在派生類BigNum
重新定義operator*
函數,該函數最初在Vector
類中定義為朋友。 具體來說,我想調用Vector
版本的operator*
,然后在BigNum
的operator *中對該操作的結果做一些其他事情。 這是該結構的一小段(再次感謝@lemmes來幫助實現這一點):
template<typename T>
class Vector
{
private:
std::vector<T> base;
public:
Vector();
Vector(const std::vector<T> vec);
Vector(const Vector& vec);
template<typename T1, typename T2>
friend auto operator*(const Vector<T1>& lhs, const Vector<T2>& rhs) -> Vector<decltype(std::declval<T1>() * std::declval<T2>())>;
};
template<typename T1, typename T2>
auto operator*(const Vector<T1>& lhs, const Vector<T2>& rhs) -> Vector<decltype(std::declval<T1>() * std::declval<T2>())>
{
typedef decltype(std::declval<T1>() * std::declval<T2>()) T3;
assert(lhs.base.size() == rhs.base.size());
Vector<T3> result;
result.base.reserve(lhs.base.size());
std::transform(lhs.base.begin(), lhs.base.end(), rhs.base.begin(), std::back_inserter(result.base),
[](const T1& e1, const T2& e2) { return e1 * e2; });
return result;
}
class BigNum : public Vector<int>
{
public:
BigNum();
BigNum(const std::vector<int> init);
~BigNum();
BigNum operator*(const BigNum& rhs);
};
#endif
BigNum BigNum::operator*(const BigNum& rhs)
{
// How can I call Vector's operator* (a friend of the Vector class)
// and then do other stuff in here?
}
#include "BigNum.h"
int main()
{
int arr1[] = {1,2,3,4,5};
int arr2[] = {10,20,30,40,50};
std::vector<int> vec1 (arr1, arr1 + sizeof(arr1) / sizeof(arr1[0]));
std::vector<int> vec2 (arr2, arr2 + sizeof(arr2) / sizeof(arr2[0]));
BigNum bn1(vec1), bn2(vec2);
bn1 * bn2; // want to call BigNum's operator* here
return 0;
}
我顯然不能做類似Vector::operator*
事情,因為它是一個朋友。 提前致謝!
您可以編寫static_cast<Vector<int>&>(bn1) * static_cast<Vector<int>&>(bn2)
來調用矢量的重載運算符。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.