[swift-evolution] protocol-oriented integers (take 2)

[David Sweeris]

> On Jan 25, 2017, at 10:03, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Stephen Canon wrote that Arithmetic should refine ExpressibleByIntegerLiteral because of certain mathematical properties of rings. In that case, 0 and 1 would just be spelled in that way. Otherwise, +1.
>> On Wed, Jan 25, 2017 at 11:38 Anton Mironov via swift-evolution <swift-evolution at swift.org> wrote:
>> Hi everyone,
>> 
>> I want to suggest a tiny extension to an Arithmetic protocol. It would be nice to have an additive identity and a multiplicative identity constants. Basically zero and one.
>> 
>> ```
>> protocol Arithmetic {
>>   /* ... */
>>   static var zero: Self { get }  // additive identity: (value + .zero) == value
>>   static var one: Self { get }   // multiplicative identity: (value * .one) == value
>> }
>> ```
>> 
>> These constants will ease implementation of math structures: vectors, matrices and etc.
>> I’m sorry if I’m duplicating someone’s suggestion. It is really hard to search for something in a long thread.

There is some merit in having them be declared as static properties... If it's a non-trivial process to initialize a type, it might be worth it to have a static property that either provides the storage directly or just returns a fileprivate value declared outside the type.

- Dave Sweeris
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