How to overload the Assignment operator so that the Original Objects's values are unchanged?

Question

I have a Matrix Class with a following function:

template<class M>
class Matrix
{
private:
int r,c;
M **mat;
public:
Matrix(int row=1,int col=1):r(row),c(col)
{
mat = new M*[r];
for (int i = 0; i < r; ++i)
{
mat[i] = new M[c];
for (int j = 0; j < c; ++j)
mat[i][j] = 0;
}
}
Matrix(initializer_list<initializer_list<M>> lst) :
Matrix(lst.size(), lst.size() ? lst.begin()->size() : 0)
{
int i = 0, j = 0;
for (const auto& l : lst)
{
for (const auto& v : l)
{
mat[i][j]=v; ++j;
}
j = 0;
++i;
}
}
Matrix operator=(const Matrix Te)
{
r=Te.r;
c=Te.c;
mat=Te.mat;
return *this;
}
///Many Other Useful Functions...
};

Now, I try to perform the following operations:

Matrix<ld>a(3,3),b(3,3);
cin>>a;
b=a;
b(3,3)=24.6;
cout<<a<<b;

But, the operation b(3,3)=24.6 changes the element at 3,3 in a as well to 24.6, which I didn't want to happen. So how can I repair the = overload so that the oriiginal values remain the same?

Why is this definition changing a as well?

Answer 1

I am going to have so many notes from aloisia and you Kinshuk

Answer 2

:) you can do it! wish i could help. but you are well ahead of me in learning

Answer 3

On correcting that and visualizing, I saw that both matrices now use the same pointer mat...
I don't understand how both got the same links...

Answer 4

It is done!

Thank You ‎ɐısıօլɐ!

I retried using a for loop instead of mat=Te.mat, and it worked perfectly!

Here is the code:

Matrix& operator=(const Matrix& Te)
{
if (this == &Te)
return *this;
r=Te.r;
c=Te.c;
for(int i=0;i<r;i++)
for(int j=0;j<c;j++)
mat[i][j]=Te.mat[i][j];
return *this;
}

Answer 5

You're great...

Answer 6

Check out my beta version :

https://code.sololearn.com/cq24J951TxgI/?ref=app

It would've never been possible without your help...

Answer 7

I get an error on marking a as const.
That - cannot bind ostream lvalue to rvalue reference...

Answer 8

That is strange ... if you try to declare a as const or constexpr, would that change something? Maybe your assigning the pointer and not copying it, so you're basically operating on the same matrix

Answer 9

Matrix& operator=(const Matrix& Te) /// Assigns M2 with the values of M1
{
if(this=&Te)
return *this;
r=Te.r;
c=Te.c;
mat=Te.mat;
return *this;
}

Even this Fails...

I'm following these steps currently:

1)Take a const-reference for the argument (the right-hand side of the assignment).
2)Return a reference to the left-hand side, to support safe and reasonable operator chaining. (Do this by returning *this.)
3)Check for self-assignment, by comparing the pointers (this to &rhs).

Answer 10

I tried assigning values using a simple for loop, but that failed as well...

Answer 11

@jay
Thank You!

Answer 12

https://www.sololearn.com/Discuss/388679/?ref=app if you have one file it might work, if you put the main file in there

Answer 13

I get this on uploading my entire code (>2000 lines)

Server error! Your code might be too long for this tool. Shorten your code and re-try.

Ill retry with just the useful part...

Answer 14

I knew it (with the pointer) glad it works now, always happy to help 🤗

Answer 15

I'm not that great, you figured it mostly out on your own :)

Answer 16

maybe try to put your code into the visualizer I posted earlier to see what your code does?

Answer 17

visualizer?
Where?

I am unable to find that...
Please upload it again...