[swift-evolution] Proposal: An Either Type in the STL

Ilias Karim ilias.karim at gmail.com
Wed Dec 9 17:32:40 CST 2015

Hi Robert,

I agree with your recommendation of a generic Either type.

However, I find your use of “Right” as the “Correct” value (whatever that means) of an instance of an Either type a little perplexing. While clever, it is exactly the kind of convention that easily leads to misunderstandings about the nature of the type itself ie. is it right and left or wrong and correct? At least that is my first impression after scanning your code.


> On Dec 9, 2015, at 3:06 PM, Developer via swift-evolution <swift-evolution at swift.org> wrote:
> It’s high time the STL admitted some kind of disjoint union type, at the very least because it’s such a minor addition it seems a shame to leave it out.  Whatever feelings one may have about `throws`, the lack of standardizing on a datatype representing choice has caused the community to get creative and create many disjoint implementation of the same concept over and over and over again.  To that end, I propose the STL ship with an Either type; We at TypeLift have already got our own we’d like to model it on (https://github.com/typelift/Swiftx/blob/master/Swiftx/Either.swift#L16).
> ~Robert Widmann (CodaFi)
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