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

[Ted F.A. van Gaalen]

( 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.