You could use a pair of:
- a map and
- a list of weak pointers to keys with a count of present items and deleted items (you would compact the list whenever there are more deleted items than present items)

Why the counts: removing items from the list on deletion is too slow.
Why the weak pointers: using keys directly could increase their lifetime after they have been deleted from the map.
If you don't need deletion, just a list of keys is fine.

On Thu, Jul 14, 2016 at 2:44 PM, Christoph Höger <christoph.hoeger@tu-berlin.de> wrote:
Am 14.07.2016 um 20:35 schrieb Jesper Louis Andersen:
> Hi,
>
> Could you give some small example of what you want or a more precise
> definition? I can think of at least 3 ways to parse meaning out of
> "gives keys in order of insertion", and I don't know which you might want.

What I mean is that a map that is created by consecutive Map.add
applications, yields the keys in the order of the add() applications, i.e.

Map.keys (Map.add k_n v_n (Map.add k_(n-1) v_(n-1) (Map.add ... (Map.add
k_1 v_1 Map.empty))))) =!= [k_1; ...; k_(n-1); k_n]

it could also yield [k_n; k_(n-1); ... ;k_1], that does not matter that
much.





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Christoph Höger

Technische Universität Berlin
Fakultät IV - Elektrotechnik und Informatik
Übersetzerbau und Programmiersprachen

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Tel.: +49 (30) 314-24890
E-Mail: christoph.hoeger@tu-berlin.de

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