set

Overview ¶

Package set provides a generic set for comparable types.

Set's underlying type is map[T]struct{} -- the same representation the Go working group chose for the proposed container/set.Set (golang/go#69230) -- so it can be ranged over and used anywhere a map is accepted, and an existing map[T]struct{} (or a named type over it) converts to a Set at zero cost. The zero value supports read operations (Contains, Len, All, Equal, String); construct via Of, Collect, or make before calling a mutator, the same as an uninitialized Go map:

var z Set[string]
z.Contains("x") // false, no panic
z.Insert("x")   // panics: assignment to entry in nil map

Set is not safe for concurrent use.

Coming from deckarep/golang-set, the migration is largely a rename:

Add          -> Insert
Remove       -> Delete
Cardinality  -> Len
Iter/Each    -> All

package main

import (
	"fmt"

	"github.com/getoutreach/gobox/pkg/set"
)

func main() {
	a := set.Of("x", "y")
	b := set.Of("y", "z")
	fmt.Println(set.Sorted(a.Union(b)))
	fmt.Println(set.Sorted(a.Intersection(b)))
	fmt.Println(set.Sorted(a.Difference(b)))
}

Output:
[x y z]
[y]
[x]

package main

import (
	"fmt"

	"github.com/getoutreach/gobox/pkg/set"
)

func main() {
	s := set.Of("x", "y", "z")
	fmt.Println(s.Len())
}

Output:
3

package main

import (
	"fmt"

	"github.com/getoutreach/gobox/pkg/set"
)

func main() {
	s := set.Of("x")
	for v := range s.All() {
		fmt.Println(v)
	}
}

Output:
x

package main

import (
	"fmt"

	"github.com/getoutreach/gobox/pkg/set"
)

func main() {
	s := set.Of("x", "y")
	fmt.Println(s.Contains("x"))
	fmt.Println(s.Contains("z"))
}

Output:
true
false