Home How to implement an operator in a derived class using the same operator that is already implemented in the base class?

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How to implement an operator in a derived class using the same operator that is already implemented in the base class?

byMR

July 16, 2023

Given these classes:

class Matrix{
//...
public:
   Matrix(int row, int column) {
     ...
   };
   Matrix operator+(const Matrix &matrix) const{
   ...
   }
};

class MatrixSquare : public Matrix{
//...
public:
   MatrixSquare(int size) {
     ...
   };
   MatrixSquare operator+(const MatrixSquare &matrix) const{
     ??????
   }
};

I’m trying to implement MatrixSquare operator+ by using Matrix::operator+. But Matrix::operator+ returns Matrix.

Do I have to create the copy constructor MatrixSquare(const Matrix &matrix) ?

>Solution :

You can use the recurring template pattern and don’t need to implement the operator in the child

template <typename Child>
class Matrix {
//...
public:
   Matrix(int row, int column) {
     ...
   }
   Child operator+(const Child &matrix) const {
   ...
   }
};

class MatrixSquare : public Matrix<MatrixSquare> {
//...
public:
   MatrixSquare(int size) : Matrix(size, size) {
     ...
   }
};