Question

I have a class which contains a few boost::numeric::ublas::matrix’s within it. I would like to overload the class’s operators (+-*/=) so that I can act on the set of matrices with one statement.

However this seems to require temporary instances of my class to carry values around without modifying the original class. This makes sense to me, however, when I create a new instance within the function and return it I get:

warning: reference to local variable ‘temp’ returned

I’m pretty new to c++ and the examples of operator overloading seem to all return new temporary objects. I would also like to avoid the overhead in instantiating new matrix’s, which leads me towards looping over all elements. How should I go about this? Performance is a concern.

Answer 1

If you’re using boost already, I’d strongly suggest using boost::operators along with your example.

You’ll get several benefits:

1. You’ll only need to overload the +=/-=/= operators, and get the +/-/ operators for free.
2. You’ll have a optimal implementation of the freely implemented operators.
3. You’ll get rid of the problem you posted, because you’ll be implementing the = versions, which require less design.