How to implement a simple set data structure in golang

set.go

type Set struct {
	list map[int]struct{} //empty structs occupy 0 memory
}

func (s *Set) Has(v int) bool {
	_, ok := s.list[v]
	return ok
}

func (s *Set) Add(v int) {
	s.list[v] = struct{}{}
}

func (s *Set) Remove(v int) {
	delete(s.list, v)
}

func (s *Set) Clear() {
	s.list = make(map[int]struct{})
}

func (s *Set) Size() int {
	return len(s.list)
}

func NewSet() *Set {
	s := &Set{}
	s.list = make(map[int]struct{})
	return s
}

//optional functionalities

//AddMulti Add multiple values in the set
func (s *Set) AddMulti(list ...int) {
	for _, v := range list {
		s.Add(v)
	}
}

type FilterFunc func(v int) bool

// Filter returns a subset, that contains only the values that satisfies the given predicate P
func (s *Set) Filter(P FilterFunc) *Set {
	res := NewSet()
	for v := range s.list {
		if P(v) == false {
			continue
		}
		res.Add(v)
	}
	return res
}

func (s *Set) Union(s2 *Set) *Set {
	res := NewSet()
	for v := range s.list {
		res.Add(v)
	}

	for v := range s2.list {
		res.Add(v)
	}
	return res
}

func (s *Set) Intersect(s2 *Set) *Set {
	res := NewSet()
	for v := range s.list {
		if s2.Has(v) == false {
			continue
		}
		res.Add(v)
	}
	return res
}

// Difference returns the subset from s, that doesn't exists in s2 (param)
func (s *Set) Difference(s2 *Set) *Set {
	res := NewSet()
	for v := range s.list {
		if s2.Has(v) {
			continue
		}
		res.Add(v)
	}
	return res
}

usage.go

mySet := NewSet()
fmt.Println("has 5", mySet.Has(5)) //false
mySet.Add(5)
fmt.Println("has 5", mySet.Has(5)) //true
mySet.Remove(5)
fmt.Println("has 5", mySet.Has(5)) //false

mySet.AddMulti(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

p := func(v int) bool { return v >= 5 }
subSet := mySet.Filter(p)
fmt.Println("all >= 5", subSet)

func (s *Set) iter() []int {
var keys []int
for k, _ := range s.list {
keys = append(keys, k)
}
return keys
}

and
for _, v := range mySet.iter() {
fmt.Println(v)
}

would be a nice addition

Thanks for this. I've modified it to be generic:

package set

type Set[T comparable] struct {
	list map[T]struct{} //empty structs occupy 0 memory
}

func (s *Set[T]) Has(v T) bool {
	_, ok := s.list[v]
	return ok
}

func (s *Set[T]) Add(v T) {
	s.list[v] = struct{}{}
}

func (s *Set[T]) Remove(v T) {
	delete(s.list, v)
}

func (s *Set[T]) Clear() {
	s.list = make(map[T]struct{})
}

func (s *Set[T]) Size() int {
	return len(s.list)
}

func NewSet[T comparable]() *Set[T] {
	s := &Set[T]{}
	s.list = make(map[T]struct{})
	return s
}

// AddMulti Add multiple values in the set
func (s *Set[T]) AddMulti(list ...T) {
	for _, v := range list {
		s.Add(v)
	}
}

type FilterFunc[T comparable] func(v T) bool

// Filter returns a subset, that contains only the values that satisfies the given predicate P
func (s *Set[T]) Filter(P FilterFunc[T]) *Set[T] {
	res := &Set[T]{}
	res.list = make(map[T]struct{})
	for v := range s.list {
		if !P(v) {
			continue
		}
		res.Add(v)
	}
	return res
}

func (s *Set[T]) Union(s2 *Set[T]) *Set[T] {
	res := NewSet[T]()
	for v := range s.list {
		res.Add(v)
	}

	for v := range s2.list {
		res.Add(v)
	}
	return res
}

func (s *Set[T]) Intersect(s2 *Set[T]) *Set[T] {
	res := NewSet[T]()
	for v := range s.list {
		if !s2.Has(v) {
			continue
		}
		res.Add(v)
	}
	return res
}

// Difference returns the subset from s, that doesn't exists in s2 (param)
func (s *Set[T]) Difference(s2 *Set[T]) *Set[T] {
	res := NewSet[T]()
	for v := range s.list {
		if s2.Has(v) {
			continue
		}
		res.Add(v)
	}
	return res
}