Type parameters

Context

Generics (introduced in Go 1.18) allow writing functions and types that work with any type, while preserving type safety. A type parameter is declared with square brackets: func F[T any](x T) T. The any constraint means any type is allowed.

Example

Write a generic Reverse function that works on any slice.

Code example

package main

import "fmt"

func Reverse[T any](s []T) []T {
    result := make([]T, len(s))
    for i, v := range s {
        result[len(s)-1-i] = v
    }
    return result
}

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

    strs := []string{"a", "b", "c"}
    fmt.Println(Reverse(strs))
}

Output

[4 3 2 1]
[c b a]

Useful links

• Go blog: Generics
• Go spec: Type parameters