[swift-evolution] protocol-oriented integers (take 2)
David Sweeris
davesweeris at mac.com
Wed Jan 25 12:58:00 CST 2017
> On Jan 25, 2017, at 07:59, 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.
Vectors, matrices, etc can't conform to this protocol anyway because of the * and / requirements. And while it is true that it's not uncommon to reference an all-zero matrix or vector as "0", that doesn't work for any other number... for them I think the spelling should be "additiveIdentity". It'll be easy enough to just say
protocol Addable {
static var additiveIdentity: Self {get}
...
}
extension Addable where Self: Arithmetic {
static var additiveIdentity: Self {return Self.zero}
}
IMHO, anyway.
- Dave Sweeris
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