Add zip, zip-with and zip-all functions #15
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Remove links to DRM for 'array', 'deque' and 'string'.
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| The function operates on two sequences (like :drm:`range`, | ||
| `array`, :drm:`list`, `deque` or `string`) and | ||
| transforms them in a :drm:`<sequence>` of pairs, each element from |
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I would make these references to the types: :drm:`<range>`, :drm:`<vector>`, :drm:`<list>`, :drm:`<deque>`, or :drm:`<string>`.
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I did it, in a previous commit, but wrong. Thanks.
| let b = #('a', 'b'); | ||
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| let zipped = zip(a, b); | ||
| format-out("%=", zipped); // Output: #(#(1, 'a'), #(2, 'b')) |
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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'))| :signature: | ||
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| zip-all (sequences) => (zipped) | ||
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zip-all #rest *sequences* => *zipped-sequence*
| = map; | ||
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| define function zip-all | ||
| (#rest sequences) => (zipped :: <sequence>) |
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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.
| add(zipped, map(head, seqs))) | ||
| end | ||
| end; | ||
| if (empty?(sequences)) #() else recur(sequences, #()) end |
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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 functionIt basically combines the definition of the local method and the initial call to it.
| @@ -588,3 +588,29 @@ define method precedes?(elt-1, elt-2, seq :: <sequence>, | |||
| not-found; | |||
| end block; | |||
| end method precedes?; | |||
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| define function zip | |||
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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).
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