Generics
The basics of Go generics.
The generics have finally arrived since the go 1.18. You will find here the basics on its use.
A very basic example that you will find a lot in your code. It’s the famous “Contains” in a slice that we recode each time:
package main
import "fmt"
func ContainsInt64(s []int64, v int64) bool {
for _, t := range s {
if t == v {
return true
}
}
return false
}
func ContainsFloat64(s []float64, v float64) bool {
for _, t := range s {
if t == v {
return true
}
}
return false
}
type Number interface {
int64 | float64
}
// generics houra !!!
func Contains[V Number](s []V, v V) bool {
for _, t := range s {
if t == v {
return true
}
}
return false
}
// or
func Contains[V comparable](s []V, v any) bool {
for _, t := range s {
if t == v {
return true
}
}
return false
}
func main() {
fmt.Println(ContainsInt64([]int64{1, 2, 3}, 1))
fmt.Println(ContainsFloat64([]float64{1, 2, 3}, 1))
fmt.Println(Contains([]int64{1, 2, 3}, 1))
fmt.Println(Contains([]float64{1, 2, 3}, 1))
}
Go playground: https://go.dev/play/p/xeUh3GPI3Ok.
Another example with a function to online some pointers, that works with multiple types:
package main
import "fmt"
func ToPtr[V any](v V) *V {
return &v
}
func main() {
fmt.Println(ToPtr("a"))
fmt.Println(ToPtr(1))
}
Go playground: https://go.dev/play/p/qcQB1oyCLgg.
Thanks to these generics you will find new libraries like https://pkg.go.dev/golang.org/x/exp/slices that will help you a lot.
In the slices library, you will find many functions that you used to code yourself, which are now available as generics and as a library:
package main
import (
"fmt"
"golang.org/x/exp/slices"
)
func main() {
fmt.Println(slices.Contains([]int64{1, 2, 3}, 1))
fmt.Println(slices.Contains([]float64{1, 2, 3}, 1))
}
Go playground: https://go.dev/play/p/CsnGdu_EC8Z.
You will find functions like:
ContainsCompareIndexSort
And more !