Tuple DIP

[Mark]

On Friday, 12 January 2018 at 22:44:48 UTC, Timon Gehr wrote:
> As promised [1], I have started setting up a DIP to improve 
> tuple ergonomics in D:
>
> https://github.com/tgehr/DIPs/blob/tuple-syntax/DIPs/DIP1xxx-tg.md
>
>
> This DIP aims to make code like the following valid D:
>
> ---
> auto (a, b) = (1, 2);
> (int a, int b) = (1, 2);
> ---
>
> ---
> foreach((sum, diff); [(1, 2), (4, 3)].map!((a, b) => (a + b, a 
> - b)))
> {
>     writeln(sum, " ", diff);
> }
> /+ prints:
> 3 -1
> 7 1
> +/
> ---
>
> Before going ahead with it, I'd like some preliminary community 
> input:
>
> - I'm not yet completely satisfied with the DIP.
>   (See section "Limitations".)
>   Please let me know suggestions or further concerns you might 
> have.
>
>
> - There are good example use cases missing. While I'm confident 
> I could
>   invent a few of them given a little time, I thought maybe I 
> can
>   expedite the process and make the point more convincingly by 
> asking
>   for use cases you encountered in your own code. The DIP 
> already
>   contains an example due to bearophile.
>
>
> [1] https://forum.dlang.org/post/or625h$2hns$1@digitalmars.com

Could we also support function tuples? For instance:

int sum(int a, int b) { return a+b; }
int diff(int a, int b) { return a-b; }

(int, int) f = (sum, diff) // no ";" for consistency with 
existing syntax
int (x,y) = f(1, 2); // x=3, y=-1
int (w,z) = (1, 2).f() // same as above, UFCS
int (u,v) = (1, 2).(sum, diff) // same as above, "lambda tuple"

In the last example, (sum, diff) is basically lowered to (x,y) => 
(sum(x,y), diff(x,y)).