passing discards qualifiers? overloading =...

I'm _attempting_ to overload the assignment operator so I can safely set one object equal to another.

Here's my code for the operator overloading:

Code:

---

const Matrix Matrix::operator=(const Matrix &temp)
{
  if(this == &temp)
    return *this; // to prevent bad things from happening..

  int x;
  int y;
  int r = temp.numR();
  int c = temp.numC();
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      Array[x][y] = temp.Array[x][y];
    }
  }
  return *this;
}

---

I get the following error:

matrix.cpp: In member function `const Matrix Matrix::operator=(const Matrix&)':
matrix.cpp:307: passing `const Matrix' as `this' argument of `int Matrix::numR()' discards qualifiers
matrix.cpp:308: passing `const Matrix' as `this' argument of `int Matrix::numC()' discards qualifiers

All of the examples of overloading = say that the declaration should be like so:

const Matrix &Matrix::operator=(const Matrix &temp)

but that further complicates my program, since I don't declare my objects on the heap. What to do about that if it really matters?

And here is the rest of the code for reference:

http://dydx.no-ip.com:8080/matrix.cpp
http://dydx.no-ip.com:8080/matrix.h

Thanks all!

"return *this" returns the object. use "this" instead. Anyway you could do it just as well without returning anything:

Code:

---


void Matrix:: operator=(const Matrix &temp)
{
  int x;
  int y;
  int r = temp.numR();
  int c = temp.numC();
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      Array[x][y] = temp.Array[x][y];
    }
  } 
}

---

Declare numR and numC as constant functions.

Code:

---

int numR() const {return a;}
int numC() const {return b;}

---

Then it will work

the assignment operator should return a non-const reference not an object.

well I redefined it as so:

Code:

---

Matrix &Matrix::operator=(const Matrix &temp)
{
  if(this == &temp)
    return *this; // to prevent bad things from happening..

  int x;
  int y;
  int r = temp.numR();
  int c = temp.numC();
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      Array[x][y] = temp.Array[x][y];
    }
  }
  return *this;
}

---

and I set numR and numC to const
But it causes the program to bog the system down to the point of me having to reboot.

Any ideas?

Thanks!

Cant see a problem with it. How bigs the array?

Quote:

---

Originally posted by Stoned_Coder
Cant see a problem with it. How bigs the array?

---

8x8 float array.

check the files in my original post.

I'm using the = operator to set 2 matrix objects equal to each other - neither are pointers, they are just objects.

I just tried this:

Code:

---

Matrix Matrix::operator=(Matrix temp)
{
  int x;
  int y;
  int r = temp.numR();
  int c = temp.numC();
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      Array[x][y] = temp.Array[x][y];
    }
  }
  return *this;
}

---

Which seems like it should work, but it still doesn't. it compiles but then crashes when running.

The way I understand it is it takes a Matrix as input (the object on the right of the =) and sets the object on the left of the = (this) equal to it, part by part. Then it returns the object, *this.

Whats going on here?

Another variant, same result:

Code:

---

Matrix Matrix::operator=(const Matrix &in)
{
  int x;
  int y;
  int r = in.numR();
  int c = in.numC();

  Matrix temp(r, c);
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      temp.Array[x][y] = in.Array[x][y];
    }
  }
  return temp;
}

---

There must be a problem somewhere else...

FINALLY got it to work:

Code:

---

void Matrix::operator=(const Matrix &temp)
{
  int x;
  int y;
  int r = temp.numR();
  int c = temp.numC();

  this->setR(r);
  this->setC(c);
 
  for(x = 0; x < r; x++)
  {
    for(y = 0; y < c; y++)
    {
      Array[x][y] = temp.Array[x][y];
    }
  }
}

---

And in Inverse() I had to do

temp = *this;

Anyway, it works as far as I can see. PAIN IN THE ASS getting there, but I learned some stuff along the way :)