CODEWITHSUNDEEP
c++oopinheritance
Sean Bone
Sean Bone

Reputation: 3546

Two classes with conversion methods

I have two matrix classes in C++ which inherit from the same base class MatrixType. They use different methods for storing sparse matrices, and are class templates because their entries may be of different types.

Each matrix type should have a method to allow to convert to the other type. The issue is that if I declare toCRS in the MatrixCOO class, the MatricCRS type for the argument is still undefined. How can I solve this problem?

class MatrixType { /*...*/ };

template<typename Scalar>
class MatrixCOO {
    // Private stuff...
public:
    // Public stuff...
    void toCRS(MatrixCRS & target) { // Issue is here: MatrixCRS is undefined
        // Fill target with elements from *this
    }
}


template<typename Scalar>
class MatrixCRS {
    // Private stuff...
public:
    // Public stuff...
    void toCOO(MatrixCOO & target) {
        // Fill target with elements from *this
    }
}

PS: in my understanding, even if I were to declare the class MatrixCRS before MatrixCOO, I would still be faced with the same problem in declaring MatrixCRS::toCOO (MatrixCOO &).

Upvotes: 0

Views: 42

Answers (1)

Jarod42
Jarod42

Reputation: 217293

Forward declare one, declare both, define function requiring both class definitions:

class MatrixType { /*...*/ };

template<typename Scalar> class MatrixCRS; // Forward declaration

template<typename Scalar>
class MatrixCOO {
    // Private stuff...
public:
    // Public stuff...
    void toCRS(MatrixCRS<Scalar>& target); // Just declare the method
};

template<typename Scalar>
class MatrixCRS {
    // Private stuff...
public:
    // Public stuff...
    void toCOO(MatrixCOO<Scalar>& target) {
        // ...
    }
};

// Implementation, we have both class definitions
template<typename Scalar>
void MatrixCOO<Scalar>::toCRS(MatrixCRS<Scalar> & target)
{
    // ...
}

Upvotes: 2

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