[swift-evolution] [Review] SE-0029 Remove implicit tuple splat behavior from function applications

[Andrew Bennett]

Hi plx,

Please take a look at my proposal:
    http://comments.gmane.org/gmane.comp.lang.swift.evolution/5334

It introduces tuple operators capable of doing many of the things you
suggest.

In case you missed it, you can currently do unlabel/relabel like this:


    let m = (a: 1, b: 2) as (Int,Int) as (c: Int, d: Int)

It's just not as concise.




On Sun, Feb 7, 2016 at 1:01 AM, plx via swift-evolution <
swift-evolution at swift.org> wrote:

> +1.
>
> I’m in the camp of people who would want an explicit version of this to
> make an eventual return, ideally as part of a broader suite of
> "tuple-manipulation operations”.
>
> In such a proposal I’d hope to see, for example, splatting, but also
> compiler-assistance for things like:
>
> - tuple-concatenation: (a,b)##(c,d) => (a,b,c,d)
> - tuple-flattening: (a,(b,(c,d))#flatten => (a,b,c,d)
> - tuple-rearrange: (a,b,c,d)#rearrange(($2,$1),($4,$3)) => ((b,a),(d,c))
> - tuple-relabel: (a,b,c,d)#relabel(foo:,bar:,baz:,qux:) => (foo: a, bar:
> b, baz: c, qux: d)
> - tuple-unlabel: (foo: a, bar: b, baz: c, qux: d)#unlabel => (a,b,c,d)
>
> …with the above as examples of the kinds of operations, and not really the
> syntax; whatever’s chosen, it ought to be possible — although perhaps not
> *advisable* — to write e.g.:
>
> // plz use a dedicated “zip4" in real life:
> for (a,b,c,d) in zip(zip(as,bs),zip(cs,ds)).lazy.map(#flatten) { … }
>
> …but that’s enough about tuple operations for now, I just wanted to
> illustrate some of the operations that be supported.
>
> Moving on, as I’m in favor of the proposal as it stands, I don’t have
> anything to contribute to the proposal itself.
>
> That said, I *do* think it’s unwise to infer too much from low rates of
> use for implicit tuple splatting at this time; it seems a little unfair to
> treat  “this feature doesn’t work" and "no one seems to be using it” as
> *independent* variables, here.
>
> As one such example, I implemented a large amount of a
> largely-declarative, combinator-ish “JSON parsing” library that would’ve
> made heavy use of tuple-splatting *if* it actually worked, but as splatting
> wound up seeming troublesome I gave up trying to use splatting.
>
> FWIW not having splatting doesn’t change the size of the *library* code
> very much, but makes each site-of-use substantially-larger.
>
> On Feb 5, 2016, at 12:12 PM, Joe Groff via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Hello Swift community,
>
> The review of “Remove implicit tuple splat behavior from function
> applications” begins now and runs through February 9, 2016. The proposal is
> available here:
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0029-remove-implicit-tuple-splat.md
>
>
> Reviews are an important part of the Swift evolution process. All reviews
> should be sent to the swift-evolution mailing list at
>
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
> or, if you would like to keep your feedback private, directly to the
> review manager. When replying, please try to keep the proposal link at
> the top of the message:
>
> Proposal link:
>
>
> http://github.com/apple/swift-evolution/blob/master/proposals/0029-remove-implicit-tuple-splat.md
>
> Reply text
>
> Other replies
>
>
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> Thank you,
>
> -Joe
> Review Manager
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