kol is a collection package based on Go 1.18+ Generics. It provides List, Set and Sequence like Kotlin collections package. You can operate collections with method-chaining 🔗.

• kotlin.collections
• kotlin.sequences

Out of scope

kol is not a complete reimplementation of the kotlin.collections and kotlin.sequences packages. It is implemented by utilizing Go language features.

go get github.com/ichizero/kol

package main

import (
	"fmt"

	"github.com/ichizero/kol"
)

func main() {
	seq := kol.NewSequence(1, 2, 3, 4, 5).
		Filter(func(e int) bool {
			return e < 3
		}).
		Map(func(e int) int {
			return e * 2
		}).
		Distinct().
		Drop(1).
		Take(2)
	fmt.Println(seq.ToSlice())
}

GoDoc:

List backend is a slice of Go.

Set backend is a map of Go. It seems like Kotlin & Java's HashMap, but it cannot be iterated in a sorted order.

Sequence enables us to lazy evaluation of a collection. In some cases, the process is faster than list operations.

For more details, please refer to the following documents.

• Kotlin docs: Sequence processing example

Because of the Go Generics specification, Map methods in each interface cannot convert an element type. You can use MapList, MapSet and MapSequence instead.

MapList(
    NewList(1, 2, 3).
        Map(func(e int) int {
            return e * 2
        }),
    func(e int) string {
        return strconv.Itoa(e)
    })