[swift-evolution] [pitch] remove global sqrt<T: FloatingPoint>
scanon at apple.com
Mon Jul 11 17:19:45 CDT 2016
A generic math module / protocol / whatever that provides all the math operations generically over the built-in floating point types is out of scope for the language/stdlib in Swift 3. Everyone wants it, it’s simply too late to add it (as with many other features and ponies).
N.B. “Out of scope for the language/stdlib” does not mean “you can’t do it”. This is a great opportunity for someone to provide a library solution (it is fairly simple to do so, even if there’s a good amount of boilerplate). I would even suggest that if such a library were widely used and vetted, it would form an excellent base for proposing a math module once Swift 3 closes down.
> On Jul 11, 2016, at 6:13 PM, Stephen Canon via swift-evolution <swift-evolution at swift.org> wrote:
> It wouldn’t delay code intended to operate generically at all. That code can use .squareRoot( ).
>> On Jul 11, 2016, at 6:12 PM, G B <g.c.b.at.work at gmail.com> wrote:
>> While I don’t have a strong opinion about what functions are in the global namespace and which are in a `Math` module, I’m not excited about the idea of delaying the availability of generic implementations of floating point functions.
>> How would this affect code intended to operate generically over Float and Double? I’ve made the mistake of trying to do this with some of my code and it’s remarkably painful for what I’d hoped would be a simple abstraction.
>> Right now (pre SE-0067), it takes a surprising amount of tinkering to get code to work generically across those two types. Provisions need to be added to provide `sqrt`, `sin`, `cos`, etc. While it all compiles down to the same instructions, I don’t feel it is natural to call `squareRoot()` as a method.
>> I don’t necessarily care if these functions are in the global namespace, or if they’re imported from a `Math` module. I’m also not convinced that they should be part of the core FloatingPoint protocol. `sqrt` probably should be, but the trig functions would naturally fit together in a protocol that itself conforms to FloatingPoint.
>>> On Jul 11, 2016, at 14:28 , Stephen Canon via swift-evolution <swift-evolution at swift.org> wrote:
>>> Post SE-0067 FloatingPoint provides the usual global operators, as well as a single global function:
>>> func sqrt<T: FloatingPoint>(_: T) -> T
>>> It seems out of place and lonely, and it would be nice if we can keep the default members of the global namespace to a minimum.
>>> I’d like to suggest removing this global from FloatingPoint while keeping the existing global functions for concrete types in the Darwin.C module. The square root operation would still be available for all FloatingPoint types as `.squareRoot()`.
>>> I would also plan to provide this and other math.h-ish globals in a future (post swift 3) Math module.
>>> – Steve
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