[swift-evolution] Make the first parameter in a function declaration follow the same rules as the others

[Ted F.A. van Gaalen]

oops !! Errata:
in my examples something went wrong:  here they are again, corrected:

> Always specifying  labels/names allows us also to have a simpler function syntax as well like so:
> 
>         bookList.insert( element: book  reorderBy: .authorName  dropOldVersions: true)       // no comma separators
> 
> or formatted like this for clarity : 
> 
>         bookList.insert(      element:  book  
>                                    reorderBy:  .authorName 
>                          dropOldVersions:  true                  )  
>       
> 
> 

Sorry
TedvG




TedvG
> On 12.03.2016, at 20:18, Ted F.A. van Gaalen <tedvgiosdev at gmail.com> wrote:
> 
> ( didn’t know it was on its way, so much to read here, missing things at times:
> 
> n.b. I’ve just read proposal SE-0046,
> "Establish consistent label behavior across all parameters including first labels”
> Imho it’s an improvement, but it still does not give the consistency/simplicity I would like to see)
> 
> To Jake and Erica: 
>      Just in case you'd think this is a better idea, feel free to adjust your proposal with it. thank you.
> 
>  ------------
> 
> Thank you Haravikk, 
> but I’d prefer to have a label obligatory on the first parm as well, for consistency,
> simplicity and readability.   
> Also for clarity:
>     A parameter name should not be part of a function name.
> 
> As in your second example:
> 
>> 	func insert( element:      Element   ) { … }
>> 	func insert( contentsOf: Sequence) { … }
>> 
> 
> 
> Always specifying  labels/names allows us also to have a simpler function syntax as well like so:
> 
>         func insert( element: Book inBooklist: Books reorder: true  dropOldVersions: true)       // no comma separators
> 
> or formatted like this for clarity : 
> 
>         func insert(      element:  Book   
>                              reorderBy:   .authorName 
>                   dropOldVersions:   true                      )  ->  Bool    
>         { … } 
> 
> 
> coincidentally, notice this is like in ObjC..  (which i liked) 
> 
> It also makes the logic with omitted default parameter simpler.
> and would allow an arbitrary parameter sequence in the call, if needed. 
> 
> (i've appended this possibility later)
> 
> I prefer overloading functions in this kind of cases instead of:
> 
>   insertBook(...
>   insertBooks(...
>   insertBooksFromArray(...
> 
> but maybe that’s just my personal taste.
> 
> At the moment I can’t find conflicts with any other language construct, 
> also for a new parameter list format without commas,
> does anyone?
> 
> TedvG
> 
> 
> 
> 
>> On 12.03.2016, at 19:22, Haravikk <swift-evolution at haravikk.me> wrote:
>> 
>> 
>>> On 11 Mar 2016, at 20:33, Ted F.A. van Gaalen via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> When I started using Swift (on the whole a pleasant journey)
>>> the most confusing thing to me was, and at times still is,  the parameter list,
>>> 
>>> 
>>> I would prefer:
>>> 
>>> -uniform for functions(…) AND init(…)
>>> -every parameter must be used with its name/label. Always, no exceptions.
>>> -no shortcuts. 
>>> -allow arbitrary parameter sequence.
>>> which is possible and very easy to implement when you always have to use names.
>>> -no trailing commas.
>> 
>> I agree, except for labels always being required; sometimes there’s just nothing to be gained by having a label, such as simple initialisers. Also, well-named functions ought to be clear what the first parameter is, for example:
>> 
>> 	func insert(_ element:Element) { … }
>> 
>> No-one’s really going to wonder what a value going into a .insert() method is for. However, requiring the developer to choose to add the underscore (as I did above) to enable this gives a balance between the consistency of having all parameters labelled by default, and being able to omit them where it makes sense to.
>> 
>> In other words, the parameter can be omitted if its label wouldn’t add anything useful to the call-site. There could be an argument that if .insertContentsOf() were restructured then the parameter might become necessary, resulting in the following:
>> 
>> 	func insert(element:Element) { … }
>> 	func insert(contentsOf:Sequence) { … }
>> 
>> But I think it’s still good for the API designer to have the option, as some cases just aren’t worth adding a label to (or would be redundant). It’s also handy for internal and private methods/initialisers that don’t need the extra clarity.
>