| // Copyright 2012 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| // +build ignore | |
| 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) | |
| } |