This topic caught my attention. I support the idea, I'm currently using an
extension for this.
>>Should “16.clamped(to: 0..<10)” produce 9 or 10?
>9
Sounds good.
>>What about “16.clamped(to: 0..<0)”, which is an empty range?
>For `Int`? Crash (which, until about 5 minutes ago, is what I thought would
>happen if you tried to create a range that’s empty like that). For types that
>support it, I’d say NaN or something like “nil”/“empty” is the most
>appropriate return value
Nasty but reasonable. I'd support it returning nil in this case, this would
provide a warning that the result may not be a valid number, as well as
providing this elegant range validation:
`if let index = candidate.clamped(to: array.indices) { … }`
(or a possible alternative spelling:)
`if let index = array.indices.clamp(candidate) { … }`
>>Does “16.0.clamped(to: 0..<10)” yield 10.0 or the next-smaller representable
>>Double?
>Next-smaller, IMHO. It’s not exactly semantically correct, but AFAIK that’s as
>correct as Float/Double can be.
One could argue the most ‘correct’ value here is the closest representation of
the theoretical value, `10.0 - (1 / ∞)`, which should clearly round to 10.
However, this also rounds the result back out of the range, meaning it's
unsuitable as a result. Both possibilities are, for lack of a better word, ugly.
>Mostly though I’d really like to be able to clamp to array indices, which are
>pretty much always written as a `Range`, rather than a `ClosedRange`. We could
>write the function for `Range` to only be generic over `Comparable&Integer`,
>if the floating point corner cases are too much.
> - Dave Sweeris
My conclusion also. I'd like to see this added to the standard library, if it's
in scope for Swift 4.
Sidenote: I can't help but think index validation would be better solved in
many cases by an optional-returning array subscript (`array[ifPresent:
index]`), but I've seen this solution turned down several times due to the lack
of discoverability (read: lack of Xcode autocompletion, which I originally
thought was a bug until it stayed that way for ~3 years). I'd also like to see
this feature get added in some form, eventually.
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