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exercise.tour.go
/*********************************************************/
// Exercise: Readers
// https://tour.golang.org/methods/11
package main
import "code.google.com/p/go-tour/reader"
type MyReader struct{}
func (r *MyReader) Read(b []byte) (int, error) {
n :=0
for i, _ := range b {
b[i] = 'A'
n++
}
return n, nil;
}
func main() {
reader.Validate(&MyReader{})
}
/*********************************************************/
// Exercise: rot13Reader
// https://tour.golang.org/methods/12
package main
import (
"io"
"os"
"strings"
)
type rot13Reader struct {
r io.Reader
}
func (rot *rot13Reader) Read(b []byte) (int, error) {
n, err := rot.r.Read(b)
for i, _ := range b {
b[i] = b[i] + 13
}
return n, err
}
func main() {
s := strings.NewReader("Lbh penpxrq gur pbqr!")
r := rot13Reader{s}
io.Copy(os.Stdout, &r)
}
/*********************************************************/
// Exercise: HTTP Handlers
// https://tour.golang.org/methods/14
package main
import (
"log"
"net/http"
)
type String string
type Struct struct {
Greeting string
Punct string
Who string
}
func (s String) ServeHTTP(
w http.ResponseWriter,
r *http.Request) {
if r.URL.Path == "/struct" {
b:= make([]byte, len(s))
for i := range s {
b[i] = s[i]
}
w.Write(b)
}
}
func (s *Struct) ServeHTTP(
w http.ResponseWriter,
r *http.Request) {
if r.URL.Path == "/struct" {
b:= make([]byte, len(s.Greeting)+len(s.Punct)+len(s.Who))
for i := range s.Greeting {
b[i] = s.Greeting[i]
}
off := len(b)
for i := range s.Punct {
b[i+off] = s.Punct[i]
}
off = len(b)
for i := range s.Who {
b[i+off] = s.Who[i]
}
w.Write(b)
}
}
func main() {
// your http.Handle calls here
log.Fatal(http.ListenAndServe("localhost:4000", nil))
}
/*********************************************************/
// Exercise: Images
// https://tour.golang.org/methods/16
package main
import (
"code.google.com/p/go-tour/pic"
"image"
"image/color"
"math/rand"
)
type Image struct{
w int
h int
}
// ColorModel returns the Image's color model.
func (i Image) ColorModel() color.Model {
return color.RGBAModel
}
// Bounds returns the domain for which At can return non-zero color.
// The bounds do not necessarily contain the point (0, 0).
func(i Image) Bounds() image.Rectangle {
return image.Rect(0, 0, i.w, i.h)
}
// At returns the color of the pixel at (x, y).
// At(Bounds().Min.X, Bounds().Min.Y) returns the upper-left pixel of the grid.
// At(Bounds().Max.X-1, Bounds().Max.Y-1) returns the lower-right one.
func (i Image) At(x, y int) color.Color {
return color.RGBA{uint8(rand.Intn(255)), uint8(rand.Intn(255)), uint8(rand.Intn(255)), uint8(rand.Intn(255))}
}
func main() {
m := Image{300,300}
pic.ShowImage(m)
}
/*********************************************************/
// Exercise: Equivalent Binary Trees
// https://tour.golang.org/concurrency/8
package main
import (
"code.google.com/p/go-tour/tree"
"fmt"
)
func Walk(t *tree.Tree, ch chan int) {
_walk(t, ch)
close(ch)
}
func _walk(t *tree.Tree, ch chan int) {
if t != nil {
_walk(t.Left, ch)
ch <- t.Value
_walk(t.Right, ch)
}
}
func Same(t1, t2 *tree.Tree) bool {
ch1:= make(chan int)
ch2:= make(chan int)
go Walk(t1, ch1)
go Walk(t2, ch2)
for i := range ch1 {
if i != <- ch2 {
return false
}
}
return true
}
func main() {
c:= make(chan int)
go Walk(tree.New(1), c)
for i := 0; i < 10; i++ {
fmt.Println(<-c)
}
fmt.Println(Same(tree.New(1), tree.New(1)))
fmt.Println(Same(tree.New(1), tree.New(2)))
}
/*********************************************************/
// Exercise: Web Crawler
// https://tour.golang.org/concurrency/9
package main
import (
"fmt"
)
type Fetcher interface {
Fetch(url string) (body string, urls []string, err error)
}
var dones map[string]bool
func DoCrawl(url string, f Fetcher, ch chan []string) {
body, urls, err := f.Fetch(url)
if err != nil {
fmt.Println(err)
return
}
fmt.Printf("found: %s %q\n", url, body)
ch <- urls
}
func Crawl(url string, depth int, fetcher Fetcher) {
urls := make(chan []string)
if depth <= 0 {
return
}
go DoCrawl(url, fetcher, urls)
depth -=1
dones[url] = true
for depth > 0 {
for _, u := range <- urls {
if _, done := dones[u] ; !done {
go DoCrawl(u, fetcher, urls)
dones[u] = true
}
}
depth--
}
close(urls)
return
}
func main() {
dones = make(map[string]bool)
Crawl("http://golang.org/", 4, fetcher)
}
// fakeFetcher is Fetcher that returns canned results.
type fakeFetcher map[string]*fakeResult
type fakeResult struct {
body string
urls []string
}
func (f fakeFetcher) Fetch(url string) (string, []string, error) {
if res, ok := f[url]; ok {
return res.body, res.urls, nil
}
return "", nil, fmt.Errorf("not found: %s", url)
}
// fetcher is a populated fakeFetcher.
var fetcher = fakeFetcher{
"http://golang.org/": &fakeResult{
"The Go Programming Language",
[]string{
"http://golang.org/pkg/",
"http://golang.org/cmd/",
},
},
"http://golang.org/pkg/": &fakeResult{
"Packages",
[]string{
"http://golang.org/",
"http://golang.org/cmd/",
"http://golang.org/pkg/fmt/",
"http://golang.org/pkg/os/",
},
},
"http://golang.org/pkg/fmt/": &fakeResult{
"Package fmt",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
"http://golang.org/pkg/os/": &fakeResult{
"Package os",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
}
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