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 _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
