go

how to copy contents of one slice to another slice in go


I'm doing below exercise in go.

Create a slice with four elements. Create a new slice and copy the third and fourth elements only into it.

I have return the below program

    package main

    import "fmt"

    func main() {
        var elements = make([]string, 4)
        elements[0] = "1"
        elements[1] = "2"
        elements[2] = "3"
        elements[3] = "4"
        fmt.Println(elements)

        var newElements = make([]string, 2)
        newElements = append(elements[:0], elements[:2]...)
        fmt.Println(newElements)
    }

output of my program is. But I want the newElements slice to be [3 4]-

[1 2 3 4]
[1 2]

What is wrong in my program.


Solution

  • Use the built-in copy function to copy elements from one slice to another.

    var newElements = make([]string, 2)
    copy(newElements, elements[2:])
    

    Run it on the playground

    Use slices.Clone to create the slice and copy the elements in a single statement:

    newElements := slices.Clone(elements[2:])
    

    Run it on the playground

    In versions of Go before 1.21, use append to create the slice and copy the elements in a single statement:

    newElements := append([]string(nil), elements[2:4]...)
    

    Run it on the playground.