How to create a hash set?

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1

I know that Odin doesn’t have a built-in separate hash set type, because one can simply use a map and don’t care about it’s values.

What would be the best way to declare such a map? Let’s say I want to create a set of strings:

map[string]<something>

I recall asking this on Discord and getting an answer which suggested using some “dummy” type for the map values, but I forgot which type that was. Some kind of “unit” type? (iirc there’s no such thing in Odin)

I figured I’d ask here too as this may be helpful to someone else later.

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If the set of expected values is small enough, a dynamic array where you scan over every value can work well. If I need a set that’s based on map and I don’t have any notion of how to better optimize it yet, I just use a bool as the value.

If your keys are unique, like indexes, you could use a bitmap. It works well with packed, linear keys. Bloom filters are fun to play with, on this note.

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3

To use map to create a set, just type map[string]struct{}.
When I have many sets in the same file, I tend to do

void :: struct{}
int_set: map[int]void
string_set: map[string]void

It just looks better to me, but is exactly the same, of course.

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4

Exactly! This was the trick I got recommended once.

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