Range types are not a panacea, especially combined with other arithmetic operators. There are essentially two options: [lo1, hi1) + [lo2, hi2) can result in a new type [lo1 + lo2, hi1 + hi2) and so on, or any operation reverts back to the base type. Only the former provides a static type guarantee but can be extremely annoying to use and you eventually have to constrain the type back with runtime checks. (Interval arithmetic also shares this problem.) Probably for this reason, to my knowledge, both Pascal and Ada implements the latter, which is more usable but also arguably useless: if your intermediate type is ranged you have to manually calculate correct bounds (a failure to do so will cause a runtime error), and if it's unranged there is zero guarantee even in the run time.