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

[Dave Abrahams]

on Sun Jan 15 2017, Xiaodi Wu <xiaodi.wu-AT-gmail.com> wrote:

> Given that Arithmetic also provides for multiplication and division, might
> it be wise then also to have .multiplicativeIdentity (or .one)?

I'm always wary of adding requirements that don't have a demonstrated
use-case in a generic algorithm.  What generic algorithm can use this
value?
>
> On Sun, Jan 15, 2017 at 02:47 Dave Abrahams via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>>
>> on Sat Jan 14 2017, Dave Abrahams <swift-evolution at swift.org> wrote:
>>
>> > That said, the ability to interpret integer literals as an arbitrary
>> > Arithmetic isn't used anywhere in the standard library, so I'd like to
>> > consider undoing
>> >
>> https://github.com/apple/swift/commit/de5b03ddc41be9c5ca5e15d5709eb2be069286c1
>> > and moving ExpressibleByIntegerLiteral down the protocol hierarchy to
>> > BinaryInteger.
>>
>> Oh, and I meant to add: maybe the right way for an arbitrary X modeling
>> Arithmetic to spell zero (which is needed for negation) is something
>> like
>>
>>    X.additiveIdentity
>>
>> or
>>
>>    X.zero
>>
>> in other words, via a requirement
>>
>>    static var theNameWeChoose: Self { get }
>>
>> --
>> -Dave
>>
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-- 
-Dave