You did pick a particularly nasty example for that one. I do agree that it is not so easy to read these constraints. It can also be a bit frustrating when you n

You did pick a particularly nasty example for that one. I do agree that it is not so easy to read these constraints. It can also be a bit frustrating when you need to chase down why exactly a particular line of code doesn't meet such a constraint. Tests like isInputRange are themselves fairly involved expressions and in the worst case, you end up staring at those after a template instantiation failed.