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

[Dave Abrahams]

on Wed Mar 09 2016, Tanner Nelson <swift-evolution at swift.org> wrote:

> I would agree that in following the Swift.org API Design Guidelines I've had to do a lot of `func foo(x x: Type)`.
>
> But simple functions like `.remove(element)` or `.append(element)`
> that really don't need labels are ubiquitous and would need to be
> changed to `_ x:`.
>
> I assume the goal is to have the default case be whatever developers
> will use most commonly.

Actually, having the default case be the one that's most predictable and
easiest to use has a lot of merit.  I can't tell you the number of times
where I've seen someone write

      func f(a: B, c: D)

when they've really meant

      func f(a _: B, c: D)

because the first argument is treated differently.

If you want to have some fun, though, count the ratio of APIs with first
argument labels to APIs without them in the proposed SDK revisions ;-)

>> On Mar 9, 2016, at 3:15 PM, Jose Cheyo Jimenez via swift-evolution
>> <swift-evolution at swift.org> wrote:
>> 
>> +1 Yes
>> 
>> the current solution makes me wish we still have the # from swift 1 ;)
>> 
>> 	func foo(x x: Int, y: Int) // Swift 2
>> 	func foo(#x: Int, y: Int) // Swift 1
>> 
>> 
>>> On Mar 9, 2016, at 10:58 AM, Joe Groff via swift-evolution
>>> <swift-evolution at swift.org
>>> <mailto:swift-evolution at swift.org>>
>>> wrote:
>>> 
>>> Our accepted naming guidelines have embraced first argument labels
>>> for functions and methods. This weakens our justification for
>>> making the first parameter declaration in a `func` declaration
>>> behave differently from the others, implicitly being unlabeled. It
>>> seems pretty clear to me we should make all of the parameter
>>> declarations behave uniformly:
>>> 
>>> func foo(x: Int, y: Int) // Should declare foo(x:y:), instead of foo(_:y:)
>>> func foo(_ x: Int, y: Int) // Explicitly declares foo(_:y:)
>>> 
>>> This would also make `init` and `func` parameters behave
>>> consistently, which is nice. There may still be hope for our
>>> keyword argument rules to one day be shorter than the Smalltalk
>>> spec…
>>> 
>>> -Joe
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> <mailto:swift-evolution at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

-- 
-Dave