[swift-evolution] Pitch: Compound name `foo(:)` for nullary functions

[Patrick Pijnappel]

I'm personally in favor of foo(_), as the number of colons currently lines
up directly with the number of arguments, and it'd be good to keep it that
way.

In general though I'm very in favor of requiring the parentheses, as the
ambiguity between unparenthesized references to functions and properties
can be quite confusing/annoying.

On Wed, Feb 22, 2017 at 6:35 PM, David Hart via swift-evolution <
swift-evolution at swift.org> wrote:

>
>
> On 22 Feb 2017, at 08:05, Jacob Bandes-Storch via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Evolutioniers,
>
> *Compound name syntax* — foo(_:), foo(bar:), foo(bar:baz:) — is used to
> disambiguate references to functions. (You might've used it inside a
> #selector expression.) But there's currently no compound name for a
> function with no arguments.
>
>     func foo() {}  // no compound syntax for this one :(
>     func foo(_ bar: Int) {}  // foo(_:)
>     func foo(bar: Int) {}  // foo(bar:)
>     func foo(bar: String, baz: Double) {}  // foo(bar:baz:)
>
> Given these four functions, only the first one has no compound name
> syntax. And the simple reference "let myfn = foo" is ambiguous because it
> could refer to any of the four. A workaround is to specify a contextual
> type, e.g. "let myfn = foo as () -> Void".
>
> I filed SR-3550 <https://bugs.swift.org/browse/SR-3550> for this a while
> ago, and there was some discussion in JIRA about it. I'd like to continue
> exploring solutions here and then write up a formal proposal.
>
> To kick off the discussion, *I'd like to propose foo(:) for nullary
> functions.*
>
> Advantages:
> - the colon marks a clear similarity to the foo(bar:) form when argument
> labels are present.
> - cutely parallels the empty dictionary literal, [:].
>
> Disadvantages:
> - violates intuition about one-colon-per-argument.
>
>
> This is a big disadvantage for me and will potentially be very surprising
> for newcomers.
>
> - the parallel between #selector(foo(:))and @selector(foo) is not quite
> as obvious as between #selector(foo(_:))and @selector(foo:).
>
>
> For the sake of discussion, another option would be *foo(_)*. This was my
> original choice, and I like that the number of colons matches the number of
> parameters. However, it's a little less obvious as a function reference. It
> would preclude _ from acting as an actual identifier, and might conflict
> with pattern-matching syntax (although it appears functions can't be
> compared with ~= anyway).
>
>
> This is my favorite syntax so far.
>
> Looking forward to everyone's bikeshed color ideas,
> Jacob
>
> _______________________________________________
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170222/c31ada68/attachment.html>