Class inheritance, copy constructor and set/get functions

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manpreet Tuteehub forum best answer Best Answer 2 years ago


I got the following class:

class Matrix{
    private:
        int rows;
        int columns;
        double* matrix;
    public:
        Matrix();
        explicit Matrix(int N);
        Matrix(int M, int N);
        void setValue(int M, int N, double value);
        double getValue(int M, int N);
        bool isValid() const;
        int getRows();
        int getColumns();
        ~Matrix();
        friend ostream& operator<<(ostream &out, Matrix&matrix1);

        Matrix &operator=(const Matrix &m) {
            if (rows * columns != m.rows * m.columns){
                delete [] this->matrix;
                this->matrix = new double[m.rows * m.columns];
            }
            rows = m.rows;
            columns = m.columns;
            for(int i = 0; i < rows; i++){
                for(int j = 0; j < columns; j++){
                    this->matrix[i * columns + j] = m.matrix[i * columns + j];
                }
            }
            return *this;
        }
        Matrix(const Matrix &rhs);
};

with these functions

#include 
#include "Matrix.h"
using namespace std;

//OPPGAVE 2
Matrix::Matrix(){
    matrix = NULL;
}

Matrix::Matrix(int N){
    matrix = 
                                                
                                                
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manpreet 2 years ago


What follows is hideous kludgery to satisfy an incompetent professor. Don't do this in the real world.

First, the misnamed "copy" constructor. If we weren't worried about the dimensions, we could do this (shudder):

Vector(const Matrix & other)
{
  *this = other;
}

But we must check the dimensions first. We could do it this way:

Vector(const Matrix & other)
{
  if(other.getColumns()==1)
      *this = other;
}

But some chucklehead neglected to make getColumns() const, so this results in a compiler error. We could do something truly drastic, const cast:

Vector(const Matrix & other)
{
  Matrix *p = const_cast<Matrix *>(&other);
  if(p->getColumns()==1)
      *this = other;
}

Or just something facepalmingly awful:

Vector(const Matrix & other)
{
  Matrix M(other); // notice that this is not const
  if(M.getColumns()==1)
      *this = other;
}

Do you need help with the isValid stuff?


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