[swift-evolution] [swift-evolution-announce] [Review] SE-0067: Enhanced Floating Point Protocols

Dave Abrahams dabrahams at apple.com
Wed Apr 27 13:07:03 CDT 2016

on Wed Apr 27 2016, Stephen Canon <swift-evolution at swift.org> wrote:

>> On Apr 27, 2016, at 1:54 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
>> on Tue Apr 26 2016, Chris Lattner <swift-evolution at swift.org> wrote:
>>> On Apr 26, 2016, at 7:34 PM, Tony Allevato via swift-evolution <swift-evolution at swift.org> wrote:
>>>> Would something like this be possible? Imagine protocols defined like this:
>>>>  public protocol Equatable {
>>>>      static func == (lhs: Self, rhs: Self) -> Self
>>>>  }
>>> The problem is that every type that conforms to Equatable has to
>>> provide an overload of == in order to conform.  This is exactly what
>>> having named methods as requirements solves.
>> Note that Tony is proposing to make the requirement static.  Whether
>> it's actually called “==” or isEqual is almost immaterial, because the
>> fact that it is static makes it less likely that anyone will try to call
>> it directly.  
>> However, if we allowed static operators to be defined, and called using
>> the syntax “T.==(x,y)”, as Tony has suggested, IMO it would further
>> discourage direct use, and it would avoid growing the number of
>> truly distinct spellings for the same operation.
>> That would also remove many instances of “formXXX” methods that
>> currently cause many people discomfort.  Whether that's a win or not
>> depends on whether you view widespread discomfort with “formXXX” as a
>> nuisance or a beneficial forcing function for finding something better
>> ;-)
> Personally I like this, but t’s not totally clear how it would extend
> to mutating operations.  `T.+=(x: inout T, y: T)`?

Well, that looks like a mix between a decl and a use.  I presume you

  static func +=(x: inout T, y: T)


  T.+=(&x, y)

That seems like the obvious answer to me.

> – Steve
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