[swift-evolution] Removing enumerated?

[Erica Sadun]

> On Feb 3, 2017, at 4:20 PM, Dave Abrahams <dabrahams at apple.com> wrote:
> 
> 
> on Fri Feb 03 2017, Erica Sadun <erica-AT-ericasadun.com> wrote:
> 
>>> On Feb 3, 2017, at 2:58 PM, Ben Cohen <ben_cohen at apple.com> wrote:
>>> 
>>> 
>>>> On Feb 3, 2017, at 11:12 AM, Erica Sadun via swift-evolution <swift-evolution at swift.org
>> <mailto:swift-evolution at swift.org>> 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