Re: [m-users.] lists and sets, unordered or ordered.

Volker Wysk <[email protected]> Tue, 03 Oct 2023 22:53:59 +0200

Newsgroups	gmane.comp.lang.mercury.general
Message-ID	<[email protected]>

Hi, Sean

Your message suddenly stops in the middle of a sentence.

Volker

Am Dienstag, dem 03.10.2023 um 21:39 +0100 schrieb Sean Charles
(emacstheviking):
> I've just completed a generic typeclass based collision detection system and learned quite a bit doing it!
> 
> As I was reading the module docs, it seems that there is no 'unordered set without duplicates' unless I missed it, which is entirely reasonable.
> 
> The output from the collision detection  is two sets of integers, these are the identifiers of the missiles and the things that were hit at the moment. I now want to take this list and then set the '^hit' flag for every missile in that list, for example, the existing code will then no longer render it and remove it on the next iteration.
> 
> I used sets because they de-dupe as you go, meaning that my checking process is simply iterating two loops, m x n, m missiles and n moving targets, for now it is naive and will probably always be fine given the limited numbers of things on screen at any one time.
> 
> There seems to be no way to get an unordered, deduplicated list from a set, I can use set_unordlist but that leaves duplicates.
> 
> 
> For now I've decided to use set_unordlist, at the cost of maybe updating the same missile record more than once poost-collision detection, it's not going to kill anything really but mentally, and from a purity point of view it feels 'less optimal' than I wanted. Failing that I might just usr  list.member and use lists for everything like I did!
> 
> I just wondered what the reasons were for not having the ability to get an unsorted 
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