> On Oct 18, 2017, at 5:28 AM, Ole Begemann via swift-evolution > <swift-evolution@swift.org> wrote: > > It also seems to clash with Michael's idea > <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20171016/040544.html> > that two substitutable sequences should return true for ==.
This is a bug in Float’s implementation of Equatable, rather than a bug in Array. So long as all the elements of Array are correct wrt all the requirements of ==, then the performance optimization that compares buffer pointers shouldn’t have correctness issues like this. But Float fails to adhere to those rules – specifically reflexivity, because for `let f = 0.0/0.0`, `f == f` returns `false`. This is the motivation behind the FP part of this proposal for Swift 4, which probably needs another go-around for Swift 5: https://github.com/airspeedswift/swift-evolution/blob/fa007138a54895e94d22e053122ca24ffa0b2eeb/proposals/NNNN-ComparisonReform.md (For which I’ll open a new thread, as this one’s plenty long already :)
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