go-tour: remove cube roots exercise
Complex numbers aren't covered by the tour (yet) and this has always
been a pretty esoteric exercise. I'd like to replace it with something
more practical.
TBR=campoy
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/111480043
diff --git a/content/moretypes.article b/content/moretypes.article
index 08c3f0e..a910dac 100644
--- a/content/moretypes.article
+++ b/content/moretypes.article
@@ -250,17 +250,6 @@
.play prog/tour/exercise-fibonacci-closure.go
-
-* Advanced Exercise: Complex cube roots
-
-Let's explore Go's built-in support for complex numbers via the `complex64` and `complex128` types. For cube roots, Newton's method amounts to repeating:
-
-.image /content/img/newton3.png
-
-Find the cube root of 8, just to make sure the algorithm works. (There is a [[http://golang.org/pkg/math/cmplx/#Pow][Pow]] function in the `math/cmplx` package to check your results.)
-
-.play prog/tour/advanced-exercise-complex-cube-roots.go
-
* Congratulations!
You finished this lesson!
diff --git a/content/prog/tour/advanced-exercise-complex-cube-roots.go b/content/prog/tour/advanced-exercise-complex-cube-roots.go
deleted file mode 100644
index 076b771..0000000
--- a/content/prog/tour/advanced-exercise-complex-cube-roots.go
+++ /dev/null
@@ -1,12 +0,0 @@
-// +build OMIT
-
-package main
-
-import "fmt"
-
-func Cbrt(x complex128) complex128 {
-}
-
-func main() {
- fmt.Println(Cbrt(2))
-}
diff --git a/solutions/complexcube.go b/solutions/complexcube.go
deleted file mode 100644
index 1704f50..0000000
--- a/solutions/complexcube.go
+++ /dev/null
@@ -1,32 +0,0 @@
-// 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)
-}
