[swift-evolution] [Proposal] Random Unification

[Nate Cook]

I created a playground to explore this question, starting with a minimal subset of the proposal’s additions and building from there. The attached playground demonstrates what’s possible with this subset on the first page, then uses subsequent pages to explore how the main random facilities of the C++ STL work under this model. (In my opinion, they work pretty well!)

The subset in the playground has three main differences from the proposal:
 - It doesn't include a Randomizable protocol or a random property on numeric types.
 - It doesn't include the static random(in:) methods on numeric types, either.
 - The RandomNumberGenerator protocol doesn't have an associated type. Instead, it requires all conforming types to produce UInt64 values.

I’ve tried to include a bit of real-world usage in the playground to demonstrate what writing code would look like with these additions. Please take a look!

Nate



> On Dec 2, 2017, at 9:50 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I don’t have much to say about this other than that I think the discussion seems way too narrow, focusing on spelling rather than on functionality and composability.  I consider the “generic random number library” design to be a mostly-solved problem, in the C++ standard library (http://en.cppreference.com/w/cpp/numeric/random <http://en.cppreference.com/w/cpp/numeric/random>).  Whatever goes into the Swift standard library does not need to have all those features right away, but should support being extended into something having the same general shape. IMO the right design strategy is to implement and use a Swift version of C++’s facilities and only then consider proposing [perhaps a subset of] that design for standardization in Swift.
> 
> Sent from my iPad
> 
> On Dec 2, 2017, at 5:12 PM, Kyle Murray via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> 
>>> On Dec 2, 2017, at 6:02 PM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> Instead, we ought to make clear to users both the features and the limitations of this API, to encourage use where suitable and to discourage use where unsuitable.
>> 
>> I like that you're considering the balance here. I've been lightly following this thread and want to add my thoughts on keeping crypto and pseudorandomness out of the name of at least one random API intended for general use.
>> 
>> For someone who doesn't know or care about the subtleties of insecure or pseudorandom numbers, I'm not sure that the name insecureRandom is effectively much different than badRandom, at least in terms of the information it conveys to non-experts. To Greg's point, that's the opposite of the signal that the API name should suggest because it's what most people should use most of the time. As you say, this API is being designed for general use.
>> 
>> There's a cost to adding extra complexity to names, too. I don't think it's far-fetched to suspect that people who find insecureRandom in an autocomplete listing or search will think "Where's the plain random function?"... and then go looking for a community extension that will inevitably provide a trivial alias: func random() { return insecureRandom() }. That's the sort of adoption I'd expect from something for new programmers, like Swift Playgrounds. Someone's introduction to randomness in programming should probably involve no more than a straightforward mapping from the elementary definition, rather than forcing a teaching moment from more advanced math.
>> 
>> I think there are better places for caveat information than in the API names themselves; documentation being one clear destination. This is in contrast with Unsafe*Pointer, where the safety element is critical enough to be elevated to be more than caveat-level information. You can go really far and create really cool things before these caveats start to apply. Using randomness as a black box in an intro programming environment seems like a much more common scenario than someone attempting to roll their first crypto by only reading API names and hoping for the best.
>> 
>> -Kyle
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