Programming language: Go
Tags: Data Structures    
Latest version: v0.2.0

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Set is a useful collection but there is no built-in implementation in Go lang.


The only one pkg which provides set operations now is golang-set

Unfortunately, the api of golang-set is not good enough.

For example, I want to generate a set from a int slice

import "github.com/deckarep/golang-set"

func main() {
    ints := []int{1, 2, 3, 4}

the code above can not work, according to

cannot use ints (type []int) as type []interface{}

You can not assign any slice to an []interface{} in Go lang.


So you need to copy your elements from []int to []interface by a loop.

That means you must do this manually every time you want to generate a set from slice.

It is ugly. So I create my own set


import "github.com/zoumo/goset"

func main() {
    goset.NewSet(1, 2, 3, 4)
    // or
    goset.NewSetFrom([]int{1, 2, 3, 4})

    goset.NewSet("1", "2", "3")
    // or
    goset.NewSetFrom([]string{"1", "2", "3"})

Full API

// Set provides a collection of operations for sets
// The implementation of Set is base on hash table. So the elements must be
// hashable, functions, maps, slices are unhashable type, adding these elements
// will cause panic.
// There are two implementations of Set:
// 1. default is unsafe based on hash table(map)
// 2. thread safe based on sync.RWMutex
// The two kinds of sets can easily convert to the other one. But you must know
// exactly what you are doing to avoid the concurrent race
type Set interface {
    // Add adds all given elements to the set anyway, no matter if it whether already exists.
    Add(elem ...interface{}) error

    // Extend adds all elements in the given interface b to this set
    // the given interface must be array, slice or Set.
    Extend(b interface{}) error

    // Remove deletes all given elements from the set.
    Remove(elem ...interface{})

    // Contains checks whether the given elem is in the set.
    Contains(elem interface{}) bool

    // ContainsAll checks whether all the given elems are in the set.
    ContainsAll(elems ...interface{}) bool

    ContainsAny(elems ...interface{}) bool

    // Copy clones the set.
    Copy() Set

    // Len returns the size of set. aka Cardinality.
    Len() int

    // String returns the string representation of the set.
    String() string

    // Range calls f sequentially for each element present in the set.
    // If f returns false, range stops the iteration.
    // Note: the iteration order is not specified and is not guaranteed
    // to be the same from one iteration to the next. The index only
    // means how many elements have been visited in the iteration, it not
    // specifies the index of an element in the set
    Range(foreach func(index int, elem interface{}) bool)

    // ---------------------------------------------------------------------
    // Convert

    // ToThreadUnsafe returns a thread unsafe set.
    // Carefully use the method.
    ToThreadUnsafe() Set

    // ToThreadSafe returns a thread safe set.
    // Carefully use the method.
    ToThreadSafe() Set

    // ---------------------------------------------------------------------
    // Compare

    // Equal checks whether this set is equal to the given one.
    // There are two constraints if set a is equal to set b.
    // the two set must have the same size and contain the same elements.
    Equal(b Set) bool

    // IsSubsetOf checks whether this set is the subset of the given set
    // In other words, all elements in this set are also the elements
    // of the given set.
    IsSubsetOf(b Set) bool

    // IsSupersetOf checks whether this set is the superset of the given set
    // In other words, all elements in the given set are also the elements
    // of this set.
    IsSupersetOf(b Set) bool

    // ---------------------------------------------------------------------
    // Set Oprations

    // Diff returns the difference between the set and this given
    // one, aka Difference Set
    // math formula: a - b
    Diff(b Set) Set

    // SymmetricDiff returns the symmetric difference between this set
    // and the given one. aka Symmetric Difference Set
    // math formula: (a - b) ∪ (b - a)
    SymmetricDiff(b Set) Set

    // Unite combines two sets into a new one, aka Union Set
    // math formula: a ∪ b
    Unite(b Set) Set

    // Intersect returns the intersection of two set, aka Intersection Set
    // math formula: a ∩ b
    Intersect(b Set) Set

// SetToSlice contains methods that knows how to convert set to slice.
type SetToSlice interface {
    // ToStrings returns all string elements in this set.
    ToStrings() []string
    // ToInts returns all int elements in this set.
    ToInts() []int
    // Elements returns all elements in this set.
    Elements() []interface{}