> On Feb 3, 2017, at 4:20 PM, Dave Abrahams <[email protected]> wrote: > > > on Fri Feb 03 2017, Erica Sadun <erica-AT-ericasadun.com> wrote: > >>> On Feb 3, 2017, at 2:58 PM, Ben Cohen <[email protected]> wrote: >>> >>> >>>> On Feb 3, 2017, at 11:12 AM, Erica Sadun via swift-evolution >>>> <[email protected] >> <mailto:[email protected]>> wrote: >>>> >> >>>> I believe what people *want* is `indexed` over `enumerated`, and >>>> consistently for both array and array slices. >>>> >>> >>> I don’t know if that’s true. >>> >>> Here’s an example (the only use of enumerated) from Alamofire: >>> >>> let acceptLanguage = Locale.preferredLanguages.prefix(6).enumerated().map { >>> index, languageCode in >>> let quality = 1.0 - (Double(index) * 0.1) >>> return "\(languageCode);q=\(quality)" >>> }.joined(separator: ", ") >>> >>> Here the intent is a counter, not indices. They just happen to be the same. >>> But if they’d used indexed() it would certainly hurt readability, albeit >>> midly. >>> >>> Suppose there wasn’t an enumerate or an indexed, and zipped was the >>> standard way of doing it. That might lead to another solution: >>> >>> let qualities = stride(from: 1.0, to: 0.4, by: -0.1) >>> let acceptLanguage = Locale.preferredLanguages.zipped(with: qualities).map { >>> languageCode, quality in "\(languageCode);q=\(quality)" >>> }.joined(separator: ", ") >>> >>> The use of stride here feels more what was intended, rather than >>> backing into the quality via an “index” value. And avoids any risk >>> with indexed of this getting applied incorrectly to slices. >>> >> >> I think enumerated as it stands is an attractive nuisance / moral >> hazard. Most of the language learners I interact with miss the point >> and the nuance of how it works. >> >> let list = [0, 1, 2, 3, 4] >> let slice = list[2...3] >> for (idx, value) in slice.enumerated() { >> print(idx, value) >> } >> >> I think people would not expect 0, 2 / 1, 3. I also don’t think they’d >> expect the actual outcome from a dictionary, whether index or >> enumeration because there’s no inherent semantic “enumeration” of >> dictionary values: >> >> let dict = [0:"a", 1:"b", 2:"c"] >> for (idx, value) in dict.enumerated() { >> print(idx, value) >> } >> >> 0 (2, "c") >> 1 (0, "a") >> 2 (1, "b") >> >> I’d like to see enumerated gone and I have a mild preference for >> introducing indexed, either under its own name or as a new behavior >> for enumerated (although T where T.Iterator.Element is Int) >> >> 120 gists with “enumerated”, of which a casual scan shows that almost >> none of them are actually using it meaningfully. (Take a look.) I >> think I did this API right: >> https://api.github.com/search/repositories?q=enumerate+language:swift >> <https://api.github.com/search/repositories?q=enumerate+language:swift> >> and if so, not much in repos. > > Ben's not arguing that enumerated should stay. He's just saying that > there's no good reason to provide indexed(), and I agree with that. > > -- > -Dave
And I think I just argued my way to agreeing with him. -- E _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
