Add generic set type

[KN4CK3R]

This PR adds a generic set type to get rid of maps used as sets.

[lafriks]

Why not just use Add to also add multiple? Just like you can use append adding single or multiple values

[KN4CK3R]

Add returns true if the element was added.

[lafriks]

It can still return bool and work for both use cases:

// Add adds the specified element to a set.
// Returns true if at least one element is added; false if all the elements is already present.
func (s Set[T]) Add(value ...T) bool {
        var added bool
	for _, v := range value {
		if _, has := s[v]; !has {
			s[v] = struct{}{}
			added = true
		}
	}
	return added
}

[wxiaoguang]

But it's ambiguous when reading code Add(a,b) to set [a], only b is added. What if one day there is another function Add with comment "true if every element is added". The return value for adding multiple values is meaningless

I stand the current approach.

[lafriks]

That's discutable but I won't block. For our use case single Add would be more than enough and easier to use imho

[wxiaoguang]

Yup, different frameworks have different choices. For C++ stl, pair<iterator,bool> insert(elem) vs void insert(begin, end) (like current approach), while in Java bool add(elem) vs bool addAll(elemList) (return true if the set is changed).

Personally I like the current approach 😁

[lafriks]

Would be nice to create func NewSet[T comparable]() Set[T] and use that instead of make, would make it more flexible in future imho

[KN4CK3R]

I removed the NewSet method some commits ago. Which advantages do you see?

[lafriks]

If for whatever reason we want to replace base struct for Set to some other instead of map[T]struct{}

[KN4CK3R]

That's not possible because there is code which uses for ... := range set. So if there may be another set type in future you are required to change these places too.

[lafriks]

That's not possible because there is code which uses for ... := range set. So if there may be another set type in future you are required to change these places too.

why .Values() is not used there?

[wxiaoguang]

why .Values() is not used there?

It copies the keys into a new array, it's inefficient