From e26ef31903fedd79d883ab9cb98bb14331fecf8b Mon Sep 17 00:00:00 2001
From: "Stephen M. McQuay" <smcquay@fusionio.com>
Date: Thu, 2 Aug 2012 17:48:46 -0600
Subject: [PATCH] added cmplx cube example

---
 exercises/04-cube/go.go | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 exercises/04-cube/go.go

diff --git a/exercises/04-cube/go.go b/exercises/04-cube/go.go
new file mode 100644
index 0000000..33d0060
--- /dev/null
+++ b/exercises/04-cube/go.go
@@ -0,0 +1,23 @@
+package main
+
+import (
+	"fmt"
+	"math/cmplx"
+)
+
+const threshold = 1e-5
+
+func Cbrt(x complex128) (z complex128) {
+	z = x
+	for delta, last := 1e9, z; delta > threshold; last = z {
+		z -= (z*z*z - x) / (3 * z * z)
+		delta = cmplx.Abs(z - last)
+	}
+	return
+}
+
+func main() {
+	n := 12392.13 + 1982i
+	fmt.Println("calculated ", Cbrt(n))
+	fmt.Println("expected   ", cmplx.Pow(n, 1/3.0))
+}