> On Nov 8, 2017, at 12:20 PM, Tino Heth <2...@gmx.de> wrote: > > >> This is a wonderful example! But it’s an argument for a different discussion >> (of general usefulness of implicit optional promotion). Thanks to the >> optional promotion, what the closure returns is not nil, but instead is >> .some(nil), and that is not filtered out. > My point is: The proposed filterMap isn’t a combination of map and filter at > all — or can you build it just out of map & filter, like flatMap is > constructed from map & flatten? https://github.com/apple/swift/blob/master/stdlib/public/core/FlatMap.swift#L49 <https://github.com/apple/swift/blob/master/stdlib/public/core/FlatMap.swift#L49>
It *is* a combination of map and filter. It is purely for performance we don’t do the same thing on any Sequence, because that will allocate a temporary array or two.
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
