Had fun making a type-safe value-oriented collection view data source in Swift today.
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I think you want countElements; it counts random-access collections in O(1) and others in O(N).
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Oh dang! Lovely.
But what if I want to implement my own collection, for which there's a reasonable O(1) count()? :/
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Also: how does it do this for an arbitrary CollectionType (i.e. non-Array) whose index is a RandomAccessIndexType?
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Minor magic. I don't want to endorse it b/c we want to do better, but very close to 's nshipster.com/swift-default-
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That does mean it will do the right thing if your custom collection uses RandomAccessIndexType!
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Oh. Uh. Interesting. I don't understand: say I make my own CollectionType where Index is Int. How does countElements() count?
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distance(collection.startIndex, collection.endIndex) → *magic* → collection.startIndex.distanceTo(collection.endIndex)
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