Darren Duncan wrote: > In reply to Jon Lang, > > What I'm proposing here in the general case, is a generic collection type, > "Interval" say, that can represent a discontinuous interval of an ordered > type. A simple way of defining such a type is that it is a "Set of Pair of > Ordered", where each Pair defines a continuous interval in terms of 2 > ordered end-points, and the whole set is discontinuous (or replace Pair with > 2-element Seq).
Note that you lose the distinction between inclusive and exclusive endpoints if you do this. That is one benefit that Range has over Pair: Range _does_ keep track of whether its endpoints are inclusive or exclusive. The main problem with Range is that it is (usually?) enumerable - which is generally considered to be a feature, but which gets in the way in the case of using it to represent a continuous interval. Thus my suggestion of somehow doing away with the enumerability if the step size is zero. As such, I'd be inclined to define Interval as a Range-like role that isn't enumerable, representing a continuous span between its lower and upper boundaries. A "disjoint interval" would be a role that usually delegates to an internal Set of Interval of Type, except when it needs to do otherwise in order to resemble a Set of Type. -- Jonathan "Dataweaver" Lang
