[swift-users] How does "Sequence.joined" work?

[Adrian Zubarev]

Moving this thread to the correct mailing list.


Am 8. August 2017 um 06:36:18, Félix Cloutier via swift-evolution (swift-evolution at swift.org) schrieb:

All this means is that `joined()` does not create an array that contains the new result. It's only as magic as the COW semantics on arrays.

Le 7 août 2017 à 21:12, Daryle Walker via swift-evolution <swift-evolution at swift.org> a écrit :

I was looking at random items at SwiftDoc.org, and noticed the “FlattenBidirectionalCollection” structure. It helps implement some versions of “joined” from Sequence (probably when the Sequence is also a BidirectionalCollection). The directions for the type state that “joined” does not create new storage. Then wouldn’t it have to refer to the source objects by reference? How; especially how does it work without requiring a “&” with “inout” or how it works with “let”-mode objects? Or am I misunderstanding how it works behind the covers?

(If there is a secret sauce to have one object refer to another without “&”/“inout”/“UnsafeWhateverPointer”, I like to know. It may help with implementing an idea. The idea involves extending the language, so “compiler magic” that the user can’t access is OK; I’d just claim to use the same sauce in my proposal.)

— 
Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT mac DOT com 

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