A Tour of Go - Advanced Exercise: Complex cube roots http://tour.golang.org/#48

complex_cube_roots.go

package main

import (
    "fmt"
    "math/cmplx"
)

const e = 1e-10

func Cbrt(x complex128) complex128 {
    /*
    For cube roots, Newton's method amounts to repeating:
    z = z - (z*z*z - x) / (3 * z*z)
    */
    z := x
    for {
        new_z := z - ((cmplx.Pow(z, 3) - x) / (3 * cmplx.Pow(z, 2)))
        if cmplx.Abs(new_z - z) < e {
            return new_z
        }
        z = new_z
    }
}

func main() {
    x := complex128(2.0)
    fmt.Println(Cbrt(x))
    fmt.Println(cmplx.Pow(x, 1/3.0))
}