How to model sets?

Dodo_87

For my current project, I need a set of elements (of an enum) . The best approach I could find online was to use a Dictionary as follows:

var my_set = {
    elem: true,
    another_elem: true,
}

So the "contains" operation is equal to my_set.has(elem). The number of elements can be retrieved via my_set.size(). You can add and remove elements (my_set.erase() and my_set.set()).

This can work fine, but is far away from a real set data type an error prone. For example my_set[elem] = false would not remove the element elem. There is no union() or intersection()method and so on.

What kind of data structure do you use, if you need a set?

Moreover:
Is there a need to have a data type Set? (What about Stacks? Queues? All sort of collections?)

DaveTheCoder

In GDScript, I think that Dictionary is the closest thing to a Set.

The Set elements would be the Dictionary keys. The values don't matter, and could be any type, such as int or bool.

You would need to implement operations such as union, intersection and difference, as functions.

You could encapsulate it in a class, with the Dictionary as a class property and the Set operations as class methods.

Since GDScript doesn't support generics (types as class and function parameters), you would need a different class for each Set element type. Maybe you could use Variant, but then there would no compile-time type-checking.

Dodo_87 Is there a need to have a data type Set? (What about Stacks? Queues? All sort of collections?)

GDScript is designed as a simple, built-in scripting language. I guess it's debatable how far to go in adding features, or whether to replace it by an existing feature-rich language such as C# (which is already an option), Kotlin, Dart or Swift.

xyz

Dodo_87 Set can be seen as a hashmap that requires each key to be the same as its value. So in gdscript you can wrap a dictionary and implement this constraint onto it.

kuligs2

why not use arrays? they are faster than dict?

Also you could write helper functions that do the erease(), or has(). if you just keep elements in array.. if you have elements with properties then it gets complicated

DaveTheCoder

kuligs2 why not use arrays? they are faster than dict?

No, they're slower.

With an array, searching for an element requires traversing the array.

Removing an element requires shifting down all the later elements.

Adding an element requires checking all of the elements to see if it's already in the array.