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

Stephen Canon scanon at apple.com
Wed Apr 27 13:03:55 CDT 2016

> 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)`?

– Steve

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