That’s the point. Using “Int.random(in: 0...9)” gives you a result that has an equal chance of being any integer between zero and nine, while “Int.random % 9” does not.
On Fri, Nov 17, 2017 at 17:30 Jonathan Hull <[email protected]> wrote: > Just to play devil’s advocate, wouldn’t they see random(in:) in the > autocomplete when typing ‘random’? > > Thanks, > Jon > > On Nov 17, 2017, at 3:09 PM, Xiaodi Wu via swift-evolution < > [email protected]> wrote: > > On Fri, Nov 17, 2017 at 10:10 AM, Gwendal Roué via swift-evolution < > [email protected]> wrote: > >> >> > Le 17 nov. 2017 à 16:04, Alejandro Alonso via swift-evolution < >> [email protected]> a écrit : >> > >> > If we go back to your example, you never call FixedWidthInteger.random >> either, you call range.random. Does this mean integer types shouldn’t have >> .random? No, because it means get a random number from it’s internal range >> (alias to (min ... max).random). I think we can all agree that >> Integer.random is a nicer api than making a range of its bounds. The same >> goes for Date.random and Color.random. >> > >> > - Alejandro >> >> Hello, >> >> I'm not random expert, but it has never happened in my developer life >> (backend & frontend app developer) that I have used a pure random value >> from the full domain of the random type. In this life: >> >> - Int.random is _always_ followed by % modulo. Unless the better >> arc4random_uniform(max) is used. >> - Color.random is _never_ used, because random colors look bad. >> - Date.random is _never_ used, because time is a physical unit, and >> random points in time do not match any physical use case. >> >> This does not mean that random values from the full domain are useless. >> Of course not: math apps, fuzzers, etc. need them. >> >> Yet a range-based API would be much welcomed by regular app developers. >> And also Array.randomElement(), Array.shuffled(), etc, because there are >> plenty naive and bad algorithms for those simple tasks. >> > > Certainly it's hard to defend Date.random (and yes, it might be useful for > a fuzzer, but that's a very niche use case--and in that case the fuzzer > should probably also generate invalid/non-existent dates, which surely > Date.random should not do). But actually, Int.random followed by % is the > much bigger issue and a very good cautionary tale for why T.random is not a > good idea. Swift should help users do the correct thing, and getting a > random value across the full domain and computing an integer modulus is > never the correct thing to do because of modulo bias, yet it's a very > common error to make. We are much better off eliminating this API and > encouraging use of the correct API, thereby reducing the likelihood of > users making this category of error. > > If (and I agree with this) the range-based notation is less intuitive > (0..<10.random is certainly less discoverable than Int.random), then we > ought to offer an API in the form of `Int.random(in:)` but not > `Int.random`. This does not preclude a `Collection.random` API as Alejandro > proposes, of course, and that has independent value as Gwendal says. > > > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution > >
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