Thread: Operator Overloading problem

It looks okay. How does it fail?

Code:

// Finds matrix with name n in vector mL; returns -1 if matrix not present
int findMatrix(vector <Matrix> &mL, string n) 
{
	Matrix temp;
	for(vector<Matrix>::iterator iT = mL.begin(); iT != mL.end(); ++iT)
	{
		temp = *iT;  
		//if strings match use std function called distance to find the number of elements between 
		//the beginning of a vector and the current itereator pos
		if(temp.getName() == n)
			return (int)distance(mL.begin(), iT);
	}
	return -1;
}

i call the assignment operator above when setting temp to my iterator thats when it heads into the operator overload and fails

Actually, now that I think about it, you should be deleting the previous data in _mat before assigning it new data. But that's not exactly a "failure", just a memory leak.

What does your copy constructor look like?

There's probably something wrong with your copy constructor, which would be needed to push Matrix's onto the vector.

But why are you using temp in findMatrix? It's an unnecessary copy operation. Just do:

Code:

if (iT->getName() == n)

Originally Posted by omGeeK

Thanks for the heads up but what do you mean by a copy constructor? All i have is a default constructor

You have a copy constructor too, since you did not disable it. Generally, whenever you need to define the destructor, copy constructor or the copy assignment operator, you need to define all three.

Why not use std::vector?

Originally Posted by omGeeK

Vector for what?

To store the data. This way, you would not need to define the copy constructor, copy assignment operator or destructor, unless you need to do some other special things in them.

Originally Posted by omGeeK

Thanks for the heads up but what do you mean by a copy constructor? All i have is a default constructor

laserlight knows a lot more about this than me, but I believe the way you've currently defined your Matrix you need a copy ctor to provide a "deep copy" of your data.

A copy ctor has a signature like:

Code:

Matrix(const Matrix& matrix);

and creates a new Matrix by copying the data from an existing matrix. It would be similar to your operator= method (but has no return statement, of course, and doesn't need to first delete any old data).

If you don't define a copy ctor then you get a default one that does a "shallow copy", simply copying each field, which is not what you want since that would mean that _mat in the copy would point to the same data as the matrix being copied instead of having its own copy of the data.

However, as laserlight said, if you used a vector inside your matrix to hold the data, then you could use the default copy ctor since a vector has a proper copy ctor defined already.

Anyway, if you're still having trouble you should post your whole program.

Originally Posted by manasij7479

@omGeek: Btw, a vector of int* s would still need a copy constructor, but vector of vector<int> s would not.

A vector<vector<int> > also would not.