On 12 January 2018 at 14:44, Timon Gehr via Digitalmars-d <digitalmars-d@puremagic.com> 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


This is nice work!
I hope this is seriously considered.

I'll add my 2c...
You discuss 'auto unpacking', can you justify the value of this?

I quite like C++ explicit unpacking (using ...), and I wouldn't be upset to see that appear here too.
Explicit unpacking would solve your breaking change with auto unpacking, but the buggest advantage of C++'s '...' statement is that the unpack can involve expressions.
  auto t = (1, 2, 3);
  f(t...);          // <-- regular expansion: f(1, 2, 3);
  f(arr[t]...);    // <-- expression expansion: f(arr[1], arr[2], arr[3]);
etc...

It's amazingly useful to perform tuple expansion on an expression involving the tuple!

So, why might implicit expansion be preferred to explicit expansion?