guard a.isSubset(of: b) else { return false }
This should be the most efficient way to do what you’re trying to do.
> Using Swift 3 I have a function that's called extremely frequently and is
> appearing regularly in Profiler runs. The function takes two
> Set<String>instances and simply attempts to determine whether all items from
> Set A are present in Set B (it's important to note that Set B may well
> contain additional items).
>
> I've attempted to approach the problem in two ways:
>
> let diff = a.subtracting(b)
> guard diff.count == 0 else { return false }
>
>
> And also by simply iterating over the contents of Set A, like so:
>
> for item in a {
> if !b.contains(item) {
> return false
> }
> }
>
>
> Both ultimately end up spending the majority of their time in
> String._compareDeterministicUnicodeCollaton(String) ->Int. Which makes sense,
> given what I'm doing - but ideally I'd like to come up with a more efficient
> way of performing the above check. Swift's String representation is
> incredibly robust, but for my needs the strings could be adequately
> represented in ASCII encoding. I've also considered storing and comparing the
> hashValue of the strings, to speed up comparisons...
>
> Hopefully this is an acceptable question for this mailing list. I'm aware
> that this may not be a Swift-specific question and could well be solved with
> a more efficient data structure or approach, but I'd really appreciate some
> input from more experienced Swift developers
> :-)_______________________________________________
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
>
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