Const & Classes With Pointers

[NickPaul]

Here is some "code" to help me explain the problem:

   class Matrix{
      double* mat; //Memory assigned by 'new double[x]'.
      double& operator()(const unsigned int row, const unsigned int col) const;
   }

   ....

   Matrix someFunc(const Matrix& a){
      a(0,0) = 1;
   }

As you can see I'm clearly changing an element of the matrix but this will not throw a "compile-time" error as I'm not changing any of the classes members. However I wish it would bring up some kind of compiler error. How can I do this?

Thanks.

Nick.

[firedraco]

Make the const version return a copy, and make a non-const version that returns a reference.

[NickPaul]

Thanks for the quick reply! Could you please show me some code on how I would go about doing that?

[Zhuge]

operator() const; should not return a reference to one of it's doubles; just make it return a normal double (a copy, as firedraco said.) Then create another operator() that isn't const that returns a reference to it's double.

[NickPaul]

Ohhh! Excellent. Thanks :) Stupid of me!

[1yR4jE8b]

You could also return a const reference