[swift-evolution] [Proposal] Shorthand Argument Renaming

[Leonardo Pessoa]

Fréderic, the idea and reasoning are good and do make sense but I'm
not 100% go on this. When I started using this syntax I felt like I
was back in PHP but once I got used it's ok. I don't see anything
wrong that justifies the change in syntax. Looking at your examples I
even think it's easier to spot "$n" in my code than ".n".


On 30 May 2016 at 13:44, Frédéric Blondiau <swift-evolution at swift.org> wrote:
> Hello,
>
> I was thinking about this, and would like to get some feedback before making my first proposal.
>
> Best regards,
>
>
> Fred.
> ---
>
> Shorthand Argument Renaming
>
>
> Introduction
>
> Swift automatically provides shorthand argument names to inline closures which cleverly allows us to write
>
>     reversed = names.sort( { $0 > $1 } )
>
> I would suggest to use another syntax, using these new “names”
>
>     reversed = names.sort( { .0 > .1 } )
>
>
> Motivation
>
> The $n notation is generally used with positional parameters using one-based numbering, $1 referring to argument 1; $2, to argument 2... with a special meaning for $0 (could be the name of the function, or the full list of parameters).
>
> This $n notation is often handy, but feels strange in Swift... like imported from UNIX scripting (but here zero-based, anyway).
>
>
> Proposed solution
>
> The .n notation is more Swift-like — as used to access Tuple members, for example.
>
>
> Detailed design
>
> Today, .0 or .1 (as any .n's) are refused by the compiler, as being not valid floating point literals.
>
> I’m not a compiler expert, but eventually fetching this error inside a closure body could easily be translated into accepting this new syntax.
>
> There can’t be conflict with other shorthands (like accessing static members using dot notation) as members can’t consist of only digits characters.
>
>
> Impact on existing code
>
> $n need to be rewritten .n
>
>
> Alternatives considered
>
> Create a default argument named “arguments” (like “error” in catch, “newValue” in setters or “oldValue” in a a didSet observer) accessed like a Tuple
>
>     reversed = names.sort( { arguments.0 > arguments.1 } )
>
> but this is (of course) much less convenient.
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution