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package dag
import (
"sync"
)
// Set is a set data structure.
type Set struct {
m map[interface{}]interface{}
once sync.Once
}
// Hashable is the interface used by set to get the hash code of a value.
// If this isn't given, then the value of the item being added to the set
// itself is used as the comparison value.
type Hashable interface {
Hashcode() interface{}
}
// hashcode returns the hashcode used for set elements.
func hashcode(v interface{}) interface{} {
if h, ok := v.(Hashable); ok {
return h.Hashcode()
}
return v
}
// Add adds an item to the set
func (s *Set) Add(v interface{}) {
s.once.Do(s.init)
s.m[hashcode(v)] = v
}
// Delete removes an item from the set.
func (s *Set) Delete(v interface{}) {
s.once.Do(s.init)
delete(s.m, hashcode(v))
}
// Include returns true/false of whether a value is in the set.
func (s *Set) Include(v interface{}) bool {
s.once.Do(s.init)
_, ok := s.m[hashcode(v)]
return ok
}
// Intersection computes the set intersection with other.
func (s *Set) Intersection(other *Set) *Set {
result := new(Set)
if s == nil {
return result
}
if other != nil {
for _, v := range s.m {
if other.Include(v) {
result.Add(v)
}
}
}
return result
}
// Difference returns a set with the elements that s has but
// other doesn't.
func (s *Set) Difference(other *Set) *Set {
result := new(Set)
if s != nil {
for k, v := range s.m {
var ok bool
if other != nil {
_, ok = other.m[k]
}
if !ok {
result.Add(v)
}
}
}
return result
}
// Len is the number of items in the set.
func (s *Set) Len() int {
if s == nil {
return 0
}
return len(s.m)
}
// List returns the list of set elements.
func (s *Set) List() []interface{} {
if s == nil {
return nil
}
r := make([]interface{}, 0, len(s.m))
for _, v := range s.m {
r = append(r, v)
}
return r
}
func (s *Set) init() {
s.m = make(map[interface{}]interface{})
}
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