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Archived project. No maintenance.

This project is not maintained anymore and is archived.. Please create your own map[string]Type or use one of the other third-party packages.

Thanks all for their work on this project.

Set GoDoc Build Status

Set is a basic and simple, hash-based, Set data structure implementation in Go (Golang).

Set provides both threadsafe and non-threadsafe implementations of a generic set data structure. The thread safety encompasses all operations on one set. Operations on multiple sets are consistent in that the elements of each set used was valid at exactly one point in time between the start and the end of the operation. Because it's thread safe, you can use it concurrently with your goroutines.

For usage see examples below or click on the godoc badge.

Install and Usage

Install the package with:

go get

Import it with:

import ""

and use set as the package name inside the code.


Initialization of a new Set

// create a set with zero items
s := set.New(set.ThreadSafe) // thread safe version
s := set.New(set.NonThreadSafe) // non thread-safe version

Basic Operations

// add items
s.Add("istanbul") // nothing happens if you add duplicate item

// add multiple items
s.Add("ankara", "san francisco", 3.14)

// remove item
s.Remove("frankfurt") // nothing happens if you remove a nonexisting item

// remove multiple items
s.Remove("barcelona", 3.14, "ankara")

// removes an arbitary item and return it
item := s.Pop()

// create a new copy
other := s.Copy()

// remove all items

// number of items in the set
len := s.Size()

// return a list of items
items := s.List()

// string representation of set
fmt.Printf("set is %s", s.String())

Check Operations

// check for set emptiness, returns true if set is empty

// check for a single item exist

// ... or for multiple items. This will return true if all of the items exist.
s.Has("istanbul", "san francisco", 3.14)

// create two sets for the following checks...
s := s.New("1", "2", "3", "4", "5")
t := s.New("1", "2", "3")

// check if they are the same
if !s.IsEqual(t) {
    fmt.Println("s is not equal to t")

// if s contains all elements of t
if s.IsSubset(t) {
	fmt.Println("t is a subset of s")

// ... or if s is a superset of t
if t.IsSuperset(s) {
	fmt.Println("s is a superset of t")

Set Operations

// let us initialize two sets with some values
a := set.New(set.ThreadSafe)
a := set.Add("ankara", "berlin", "san francisco")
b := set.New(set.NonThreadSafe)
b := set.Add("frankfurt", "berlin")

// creates a new set with the items in a and b combined.
// [frankfurt, berlin, ankara, san francisco]
c := set.Union(a, b)

// contains items which is in both a and b
// [berlin]
c := set.Intersection(a, b)

// contains items which are in a but not in b
// [ankara, san francisco]
c := set.Difference(a, b)

// contains items which are in one of either, but not in both.
// [frankfurt, ankara, san francisco]
c := set.SymmetricDifference(a, b)
// like Union but saves the result back into a.

// removes the set items which are in b from a and saves the result back into a.

Multiple Set Operations

a := set.New(set.ThreadSafe)
a := set.Add("1", "3", "4", "5")
b := set.New(set.ThreadSafe)
b := set.Add("2", "3", "4", "5")
c := set.New(set.ThreadSafe)
c := set.Add("4", "5", "6", "7")

// creates a new set with items in a, b and c
// [1 2 3 4 5 6 7]
u := set.Union(a, b, c)

// creates a new set with items in a but not in b and c
// [1]
u := set.Difference(a, b, c)

// creates a new set with items that are common to a, b and c
// [5]
u := set.Intersection(a, b, c)

Helper methods

The Slice functions below are a convenient way to extract or convert your Set data into basic data types.

// create a set of mixed types
s := set.New(set.ThreadSafe)
s := set.Add("ankara", "5", "8", "san francisco", 13, 21)

// convert s into a slice of strings (type is []string)
// [ankara 5 8 san francisco]
t := set.StringSlice(s)

// u contains a slice of ints (type is []int)
// [13, 21]
u := set.IntSlice(s)

Concurrent safe usage

Below is an example of a concurrent way that uses set. We call ten functions concurrently and wait until they are finished. It basically creates a new string for each goroutine and adds it to our set.

package main

import (


func main() {
	var wg sync.WaitGroup // this is just for waiting until all goroutines finish

	// Initialize our thread safe Set
	s := set.New(set.ThreadSafe)

	// Add items concurrently (item1, item2, and so on)
	for i := 0; i < 10; i++ {

		go func(i int) {
			defer wg.Done()

			item := "item" + strconv.Itoa(i)
			fmt.Println("adding", item)

	// Wait until all concurrent calls finished and print our set



The MIT License (MIT) - see for more details