> On Jan 25, 2017, at 07:59, Anton Mironov via swift-evolution
> <[email protected]> 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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