I believe this to be entirely sufficient as well, despite not being truly safe. It's either going to throw an error immediately or on first bad access. It makes

I believe this to be entirely sufficient as well, despite not being truly safe. It's either going to throw an error immediately or on first bad access. It makes no difference to me. I can see how the proposed solution could be "better", but I'd rather avoid the validation code and instead get the type right.