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saghm • last Sunday at 3:54 AM • 2 replies • view on HN

Yeah, returning an empty array is pretty much exactly what I would expect given the first example. It would be a lot weirder to me if you were allowed to give an end index past the last element only if the array happened to be non-empty.

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t-writescode • last Sunday at 1:25 PM

Sorry, I mis-spoke earlier, this is what I should have shared:

  [].slice(5, 100)
^-- *THIS* either returns nil or throws an exception.

Edit: Longer example:

  puts "[1, 2, 3].slice(1, 100) -> #{[1, 2, 3].slice(1, 100).to_s}"
  puts "[1, 2, 3].slice(3, 100) -> #{[1, 2, 3].slice(3, 100).to_s}"
  puts "[1, 2, 3].slice(4, 100) -> #{[1, 2, 3].slice(4, 100).to_s}"
Yields:

  [1, 2, 3].slice(1, 100) -> [2, 3]
  [1, 2, 3].slice(3, 100) -> []
  [1, 2, 3].slice(4, 100) ->
So, there is a behavior difference between "array a little too short" and "array slightly more too short" that creates unexpected behavior.

That's not a big surprise in a tiny example like this; but if you expand this out into a larger code base, where you're just being an array and you want the 100 through 110th values for whatever reason - say it's a csv. Suddenly you're having to consider both the nil case and the empty array case; but then why are they different?

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bradchris • last Sunday at 4:10 AM

Especially because in ruby

[0, nil, nil, nil, …x100, nil] is the same as [0] in terms of access.

In both cases, trying to access the 100th element (e.g. [0][100]) will give nil.