Add zip, zip-with and zip-all functions

[fraya]

No description provided.

[cgay]

I would make these references to the types: :drm:`<range>`, :drm:`<vector>`, :drm:`<list>`, :drm:`<deque>`, or :drm:`<string>`.

[fraya]

I did it, in a previous commit, but wrong. Thanks.

[cgay]

This is fine, but I prefer the following style, because it doesn't have the distraction of the format-out call.

let a = #(1, 2);
let b = #('a', 'b');
zip(a, b)
// => #(#(1, 'a'), #(2, 'b'))

[cgay]

zip-all #rest *sequences* => *zipped-sequence*

[cgay]

The name "sequences" is misleading here since this function will only work with lists. Should it work with sequences in general? (I think so.) Perhaps you can do it by calling forward-iteration-protocol on each sequence directly.

[cgay]

I am a big fan of the iterate macro, which would look something like this:

define function zip-all (#rest lists) => (zipped :: <list>)
  iterate loop (lists = lists, zipped = #())
    if (any?(empty?, lists))
      reverse!(zipped)
    else
      loop(map(tail, lists), pair(map(head, lists)))
    end if
  end iterate
end function

It basically combines the definition of the local method and the initial call to it.

[cgay]

Naming is hard, so I won't claim that this is definitely better, but one potential alternative is to call this function zip2 and call zip-all just zip so that it matches other popular languages (Python).