http://tour.golang.org/#48

48.go

package main

import "fmt"

func Cbrt(x complex128) func() complex128 {
    z := complex128(1)
    return func() complex128 {
        z=z-(z*z*z-x)/(3*z*z)
        return z
    }
}

func main() {
    cbrt2:=Cbrt(2)
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
    fmt.Println(cbrt2())
}