[roenxi]

It maps very well onto the mathematical concept of a closed interval [a, b] where a and b are endpoints of the interval though. You're adding a constraint for no logical reason and it happens to be very hard to represent in a basic type system.

> An interval where a > b is usually a programming error.

If you want it to be, sure. Anything can be a programming error if the library author feels like it. We may as well put all sorts of constraints on clamp, it is probably an error if the caller uses a large number or a negative too. It is still bad design in a theoretical sense - the clamp function throws an error despite there being an obvious non-error return value. It isn't hard to meaningfully clamp 2 between 4 and 3.