Nim: Unpacking nested tuples in for loop

[dom96]

Should we make it a requirement to include the parenthesis when unpacking tuples in for loops? This will in turn allow for this to work:

iterator foo(): tuple[x: tuple[y, z:int], y: tuple[y, z: int]] =
  yield ((1, 2), (3, 4))

for ((a, b), (c, d)) in foo():
  echo a, c

And be consistent with tuple unpacking in var/let declarations.

[def-]

I consider this uglier than what we have currently, for example for

for (i, x) in @[1, 2,3]: ...

[dom96]

I don't consider that ugly.

[reactormonk]

That will break a LOT of code, time for 2to3-style? I like the new syntax though.

[dom96]

We can allow both I guess.

[reactormonk]

And deprecate the old one? Not sure how to implement the deprecation in the parser, but it should be possible. And I currently don't see a problem with syntax ambiguities either.

[narimiran]

Superseded by #7486 (more comments and discussion there).

[nc-x]

@narimiran
I think both these issues are different.

This issue is asking for nested tuple unpacking.
But that is not supported anywhere

var ((a, b), (c, d)) = ((1,2), (3,4))                 # Parsing error

So this is kind of asking for general pattern matching support which as per Araq's opinion should be written as a macro. So this RFC has very less chances of being accepted anyways.

[narimiran]

@nc-x So your solution doesn't work for the nested tuples? Can you make it work? :)

[nc-x]

No, my patch doesn't support nested tuple unpacking. I didn't add it because the language does not support nested tuple unpacking anywhere. IDK if araq wants them in the language.
@narimiran So your best bet would be to convince @Araq ;)

[Araq]

PRs for nested tuple unpacking will be accepted.