Go 2 Generics

generics.go2

// Go 2 Playground: https://go2goplay.golang.org/
//
// Or to install the go2go tool:
// git clone https://go.googlesource.com/go goroot
// cd ./goroot
// git checkout dev.go2go
// cd ./src
// CGO_ENABLED=0 ./all.bash
// export PATH=/path/to/your/goroot/bin:$PATH
//
// go tool go2go run ./main.go2
package main

import (
	"fmt"
	"reflect"
)

func main() {
	ss := []string{"hello", "generic", "world"}
	is := []int{0, 3, 7}

	printStringSlice(ss)
	printIntSlice(is)

	printCase(ss)
	printCase(is)

	printReflect(ss)
	printReflect(is)

	printGeneric(ss)
	printGeneric(is)
}

// A specific implementation for slices of strings
func printStringSlice(list []string) {
	fmt.Println("string slice: ")
	for _, s := range list {
		fmt.Print(s, " ")
	}
	fmt.Print("\n")
}

// A specific implementation for slices of integers
func printIntSlice(list []int) {
	fmt.Println("int slice: ")
	for _, i := range list {
		fmt.Print(i, " ")
	}
	fmt.Print("\n")
}

// An implementation based on a nil interface supporting either slices of integers or strings using a case statement
func printCase(v interface{}) {
	fmt.Println("case: ")
	switch list := v.(type) {
	case []string:
		for _, s := range list {
			fmt.Print(s, " ")
		}
	case []int:
		for _, i := range list {
			fmt.Print(i, " ")
		}
	}
	fmt.Print("\n")
}

// A implementation based on a nil interface supporting slices using reflection
func printReflect(v interface{}) {
	fmt.Println("reflect: ")
	val := reflect.ValueOf(v)
	if val.Kind() != reflect.Slice {
		return
	}

	for i := 0; i < val.Len(); i++ {
		fmt.Print(val.Index(i).Interface(), " ")
	}
	fmt.Print("\n")
}

// An implementation using Go generics supporting any slice of type []T
func printGeneric[T any](slice []T) {
	fmt.Println("generic: ")
	for _, v := range slice {
		fmt.Print(v, " ")
	}
	fmt.Print("\n")
}