Compilation Errors:
- Initializer list order needs to match declaration order
- Implementation of copy constructor needs const specifier for argument
- operator[] probably shouldn't be const since one can change the list through it. It will compile with const, though, since technically the method itself doesn't change the list.
- updated op[] declaration to match definition
- in op<<, need to say rhs.size_ instead of size_

Correctness Errors:
- in op<<, the for loop should be inside the if clause
- memcpy needs to use size_ * sizeof(int), not just size_