```agemoagemo / yahoo.com wrote:
> --- Robert Klemme <bob.news / gmx.net> wrote:
>>> %w{aa bb cc dd ee ff gg hh ii jj
>> kk}.each_window(3) {|*a| p a}
>> ["aa", "bb", "cc"]
>> ["bb", "cc", "dd"]
>> ["cc", "dd", "ee"]
>> ["dd", "ee", "ff"]
>> ["ee", "ff", "gg"]
>> ["ff", "gg", "hh"]
>> ["gg", "hh", "ii"]
>> ["hh", "ii", "jj"]
>> ["ii", "jj", "kk"]
>> => ["aa", "bb", "cc", "dd", "ee", "ff", "gg", "hh",
>> "ii", "jj", "kk"]
>
> Am I the only one who thinks this seems a little
> peculiar?
>
> If I were writing something using this sort of
> functionality, I think I'd need and expect
> output something like:
>
> [nil, "aa", "bb"]
> ["aa", "bb", "cc"]
> ["bb", "cc", "dd"]
> ["cc", "dd", "ee"]
> ["dd", "ee", "ff"]
> ["ee", "ff", "gg"]
> ["ff", "gg", "hh"]
> ["gg", "hh", "ii"]
> ["hh", "ii", "jj"]
> ["ii", "jj", "kk"]
> ["jj", "kk", nil]

Well, it depends.  If, for example, you would want to make a plot that
used averaged values (i.e. to smooth the curve) you would not want to see
those lines containing nil values IMHO.

> Admittedly, it'd be hard to that reasonably with a
> variable-size window of even length. But for a
> previous-current-next arrangement, it seems to make
> more sense to say "there is no previous" with a nil
> than to basically skip the first item.

It's not that hard to do.

Kind regards

robert

```