blob: 390415e316263851978703aafe483d8c084c27e8 [file] [log] [blame] [edit]
package dag
// Set is a set data structure.
type Set map[interface{}]interface{}
// 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[hashcode(v)] = v
}
// Delete removes an item from the set.
func (s Set) Delete(v interface{}) {
delete(s, hashcode(v))
}
// Include returns true/false of whether a value is in the set.
func (s Set) Include(v interface{}) bool {
_, ok := s[hashcode(v)]
return ok
}
// Intersection computes the set intersection with other.
func (s Set) Intersection(other Set) Set {
result := make(Set)
if s == nil || other == nil {
return result
}
// Iteration over a smaller set has better performance.
if other.Len() < s.Len() {
s, other = other, s
}
for _, v := range s {
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 {
if other == nil || other.Len() == 0 {
return s.Copy()
}
result := make(Set)
for k, v := range s {
if _, ok := other[k]; !ok {
result.Add(v)
}
}
return result
}
// Filter returns a set that contains the elements from the receiver
// where the given callback returns true.
func (s Set) Filter(cb func(interface{}) bool) Set {
result := make(Set)
for _, v := range s {
if cb(v) {
result.Add(v)
}
}
return result
}
// Len is the number of items in the set.
func (s Set) Len() int {
return len(s)
}
// List returns the list of set elements.
func (s Set) List() []interface{} {
if s == nil {
return nil
}
r := make([]interface{}, 0, len(s))
for _, v := range s {
r = append(r, v)
}
return r
}
// Copy returns a shallow copy of the set.
func (s Set) Copy() Set {
c := make(Set, len(s))
for k, v := range s {
c[k] = v
}
return c
}