[swift-evolution] When to use argument labels, part DEUX
Matthew Judge
matthew.judge at gmail.com
Sun Feb 7 13:10:05 CST 2016
> Gah! Well if you'd like to post those messages here, you certainly have
> my permission. It might be good to have them as part of the public
> record.
>
> --
> -Dave
>
Dave's reply to me inline...
> on Fri Feb 05 2016, Matthew Judge <matthew.judge-AT-gmail.com> wrote:
>
> I certainly can live with these guidelines (and although I have a
> slight preference for something like move(from: a, to: b), it is only
> a _slight_ preference). However, I do have a suggested tweak to
> A. that I believe maintains clarity of guidance and covers this
> case. (See below inline)
>
>> On Feb 5, 2016, at 16:32, Dave Abrahams via swift-evolution
>> <swift-evolution at swift.org> wrote:
>>
>>
>> Given all the awesome feedback I've gotten on this thread, I went back
>> to the drawing board and came up with something new; I think this one
>> works. The previously-stated goals still apply:
>>
>> * describe when and where to use argument labels
>> * require labels in many of the cases people have asked for them
>> * are understandable by humans (this means relatively simple)
>> * preserve important semantics communicated by existing APIs.
>>
>> Please keep in mind that it is a non-goal to capture considerations we
>> think have a bearing on good names (such as relatedness of parameters):
>> it's to create simple guidelines that have the right effect in nearly
>> all cases.
>>
>> A. When arguments can't be usefully distinguished from one another, none
>> should have argument labels, e.g. min(x,y), zip(x,y,z).
>
> When arguments' _importance_ can't be usefully distinguished from one
> another, none should have argument labels or _all should have argument
> labels_, e.g. min(x,y), zip(x,y,z), move(from: a, to: b), moveTo(x: a,
> y: b)
That would also imply
move(a, b)
tracksWith(a, b)
are both OK, because the importance of a and b can't be distinguished.
It would also imply that
min(first: a, second: b)
is OK. I don't want any of these to be OK. Do you?
Even if it didn't have these problems, it's asking people to make a
judgement about importance, which makes the rule harder to apply
consistently, and the only practical effect of your proposed change
seems to be to get your preferred form for move(from: a, to: b).
>> B. Otherwise,
>>
>> 1. At the call site, a first parameter that has no argument label must
>> form part of a grammatical phrase that starts with the basename, less
>> any trailing nouns.
>>
>> print(x)
>> a.contains(b)
>> a.mergeWith(b)
>> a.addGestureRecognizer(x)
>> ^~~~~~~~~~~~~~~~~ trailing noun
>
> One other potential concern. I understand (and wholeheartedly agree)
> that GestureRecognizer should be pet of the base name here, but I'm
> not sure I see where the guidance explains it to me.
Ah, I see what you mean. The rules as written would also allow
add(gestureRecognizer: x)
Excellent point! I think the fix is to declare, in B.1., that this form
is to be preferred.
>> This phrase must have the correct semantic implications, so, e.g.
>>
>> a.dismiss(b) // no, unless a is really dismissing b
>> a.dismissAnimated(b) // no, not grammatical
>> a.dismiss(animated: b) // yes, using a label
>>
>> 2. If the first argument is part of a prepositional phrase, put the
>> parenthesis immediately after the preposition.
>>
>> a.encodeWith(b)
>> a.moveFrom(b, to: c)
>>
>> Thus, if words are required for any reason between the preposition
>> and the first argument, they go into the first argument label.
>>
>> a.tracksWith(mediaType: b, composer: c)
>> a.moveTo(x: 22, y: 99)
>>
>> Notes:
>>
>> a. I would recommend prepositions other than "with" in nearly all
>> cases, but that's not the point of these rules.
>> b. I can understand the aesthetic appeal of
>>
>> a.move(from: b, to: c)
>>
>> but I believe it is not a clear enough improvement to justify
>> additional complexity in the guidelines.
>>
>> Questions:
>>
>> 1. I'm not expecting these guidelines to make everybody optimally happy,
>> all the time, but they shouldn't be harmful. Are there any cases for
>> which they produce results you couldn't live with?
>>
>> 2. Are there any cases where you'd be confused about how to apply these
>> guidelines?
>>
>> Thanks in advance for all your valuable input!
>>
>> P.S. Doug is presently working on generating new importer results, based
>> on these guidelines, for your perusal. They should be ready soon.
>>
>> --
>> -Dave
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
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