Implement cube root with Newton's method.

go_tour_ex5_cbrt.go

package main

import (
    "fmt"
    "math/cmplx"
)

const delta = 1e-15

func Cbrt(x complex128) complex128 {
    z := complex128(1.0)
    
    for {
        d := (cmplx.Pow(z, 3) - x)/cmplx.Pow(z, 2)/3
        
        if cmplx.Abs(d) < delta {
            break
        }
        
        z -= d
    }
    return z
}

func main() {
    fmt.Println(Cbrt(2))
}