Type constraints

Context

Type constraints limit what types can be used as type arguments. The built‑in constraint any allows all types. comparable allows types that can be compared with == and !=. You can also define custom constraints using an interface.

Example

Use comparable to check if a slice contains a specific value.

Code example

package main

import "fmt"

func Contains[T comparable](slice []T, value T) bool {
    for _, v := range slice {
        if v == value {
            return true
        }
    }
    return false
}

func main() {
    ints := []int{1, 2, 3}
    fmt.Println(Contains(ints, 2)) // true
    fmt.Println(Contains(ints, 5)) // false

    strs := []string{"apple", "banana"}
    fmt.Println(Contains(strs, "banana")) // true
}

Output

true
false
true

Useful links

• Go spec: Type constraints
• Go by Example: Generics