"unsigned" doesn't express intent. It expresses implementation, maybe it expresses assumption. Ada's "Positive" or "Natural" or subtype X is Integer range Y

"unsigned" doesn't express intent. It expresses implementation, maybe it expresses assumption. Ada's "Positive" or "Natural" or subtype X is Integer range Y..Z; expresses intent (well expresses requirement really), it also enforces that constraint, so it's not merely an assumption.