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[Python-Dev] decorate-sort-undecorate

Michael Chermside mcherm at mcherm.com
Wed Oct 15 09:51:17 EDT 2003 
Tim writes:
> Almost all sorts you're likely
> to use in real life are stable in order to support this, whether it's
> clicking on an email-metadata column in Outlook, or sorting an array of data
> by a contained column in Excel.

Guido tries it out:
> I experimented a bit with the version of Outlook I have, and it seems
> to always use the delivery date/time as the second key, and always in
> descending order.

Which is simply evidence that Outlook is poorly designed, and that
Microsoft should have hired Tim to help with design specs. Although
Outlook lacks this feature, I have FREQUENTLY desired it, and been
annoyed at its absence.

Tim in a later email:
> It depends some on the current view, but I misremembered Outlook's UI
> anyway:  to get a multi-heading sort, you have to be depress the shift key
> when clicking on the 2nd (and 3rd, etc) column (and click twice (not
> double-click!) to reverse the sort order on the current column; the shift
> key applies there too if you want a multi-key sort order).

Well well... it's nice to learn that!


I find Tim's (and other's) arguments quite convincing. We can go with
a stable sort... ie, compare the keys, then fall back on stability
and NEVER try comparing the objects themselves, and I think it will
make complete sense. After all, sorting with a "key" parameter
provided is *NOT* really a DSU algorithm... it's a new sort feature
which happens to be _implemented_ using DSU. Should that new feature
sort on "just the key" (leaving ties stable) or should it sort on
"the key and then the objects themselves". I'd say both make sense,
and in fact "just the key" is more obvious to me.

-- Michael Chermside
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