code review 6585074: golang-tour: Solutions to the exercises.

gotour/solutions/complexcube.go

+package main
+
+import (
+        "fmt"
+        "math/cmplx"
+)
+
+const delta = 1e-10
+
+func Cbrt(x complex128) complex128 {
+        z := x
+        for {
+                n := z - (z*z*z-x)/(3*z*z)
+                if cmplx.Abs(n-z) < delta {
+                        break
+                }
+                z = n
+        }
+        return z
+}
+
+func main() {
+        const x = 2
+        mine, theirs := Cbrt(x), cmplx.Pow(x, 1./3.)
+        fmt.Println(mine, theirs, mine-theirs)
+}