[swift-evolution] zip3, zip4, ...

[Jacob Bandes-Storch]

zip2 (aka "zip") is present in Swift. zip3 is often useful, but not
built-in.

It can be achieved by using multiple copies of zip2:

  for (one, (two, three)) in zip(list1, zip(list2, list3)) ...

It seems like either of these could make sense:

- Put some reasonable number of implementations, like zip2...zip10, in the
standard library, using gyb.

- Have the compiler generate them on the fly as requested by the user.

Or, some alternate approaches:

- Don't do this right now, but count it as motivation for a macro system.

- Consider making Swift's pattern-matching system extensible, which might
allow custom array-based patterns, like "for [one, two, three] in
zip(list1, list2, list3)".  (I've been thinking of writing a proposal for
this anyway.)


Does anyone else care about zip3-and-higher? How do these options sound?

Jacob Bandes-Storch
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