Operator overload of << needs const; produces headache

Question

I am trying to overload operator <<, but it always need to be a const function. However, I want to change values inside this overloaded function

Answer 1

You're implementing operator<< as an inserter into our Check object here. In this case, it looks like the right solution is to just have your insertion operator actually be non-const, since it would be nonsensical to use it on a const object (because it's mutating logical object state).