golang官方指导练习(go tour exercise)

序

本文是golang官方练习的pass代码，使用了中文版的tour

循环与函数

package mainimport (    "fmt")func Sqrt(x float64) float64 {    res := 1.0    for i := 0; i < 10; i++ {        res = res - (res * res - x) / 2 / res    }    return res}func main() {    fmt.Println(Sqrt(2))}

slice

package mainimport "golang.org/x/tour/pic"func Pic(dx, dy int) [][]uint8 {    var pic [][]uint8;    for i := 0; i < dy; i++ {        var one_line []uint8        for j := 0; j < dx; j++ {            one_line = append(one_line, (uint8)(i & j))        }        pic = append(pic, one_line)    }    return pic}func main() {    pic.Show(Pic)}

map

package mainimport (    "golang.org/x/tour/wc"    "strings")func WordCount(s string) map[string]int {    count := make(map[string]int)    for _, v := range strings.Fields(s) {        count[v] = count[v] + 1    }    return count}func main() {    wc.Test(WordCount)}

斐波纳契闭包

package mainimport "fmt"// fibonacci is a function that returns// a function that returns an int.func fibonacci() func() int {    one := 0    two := 1    return func() int {         result := one        one = two        two = result + two        return result    }}func main() {    f := fibonacci()    for i := 0; i < 10; i++ {        fmt.Println(f())    }}

stringer

package mainimport "fmt"type IPAddr [4]byte// TODO: Add a "String() string" method to IPAddr.func (IP IPAddr) String() string {    return fmt.Sprintf("%v.%v.%v.%v", IP[0], IP[1], IP[2], IP[3])}func main() {    hosts := map[string]IPAddr{        "loopback":  {127, 0, 0, 1},        "googleDNS": {8, 8, 8, 8},    }    for name, ip := range hosts {        fmt.Printf("%v: %v\n", name, ip)    }}

error

package mainimport (    "fmt")type ErrNegativeSqrt float64func (e ErrNegativeSqrt) Error() string {    return fmt.Sprintf("cannot Sqrt negative number: %v", float64(e))}func Sqrt(x float64) (float64, error) {    if x < 0 {        return 0, ErrNegativeSqrt(x)    }    res := 1.0    for i := 0; i < 10; i++ {        res = res - (res * res - x) / 2 / res    }    return res, nil}func main() {    fmt.Println(Sqrt(2))    fmt.Println(Sqrt(-2))}

Reader

package mainimport "github.com/Go-zh/tour/reader"type MyReader struct{}// TODO: Add a Read([]byte) (int, error) method to MyReader.func (r MyReader) Read(p []byte) (int, error) {    for i := 0; i < len(p); i++ {        p[i] = 'A'    }    return len(p), nil}func main() {    reader.Validate(MyReader{})}

rot13Reader

package mainimport (    "io"    "os"    "strings")type rot13Reader struct {    r io.Reader}func (self rot13Reader) Read(buf []byte) (int, error) {    length, err := self.r.Read(buf)    if err != nil {        return length, err    }    for i := 0; i < length; i++ {        v := buf[i]        switch {        case 'a' <= v && v <= 'm':            fallthrough        case 'A' <= v && v <= 'M':            buf[i] = v + 13        case 'n' <= v && v <= 'z':            fallthrough        case 'N' <= v && v <= 'Z':            buf[i] = v - 13        }    }    return length, nil}func main() {    s := strings.NewReader("Lbh penpxrq gur pbqr!")    r := rot13Reader{s}    io.Copy(os.Stdout, &r)}

image

package mainimport (    "golang.org/x/tour/pic"    "image"    "image/color")type Image struct{    w int    h int}func (self Image) ColorModel() color.Model {    return color.RGBAModel}func (self Image) Bounds() image.Rectangle {    return image.Rect(0, 0, self.w, self.h)}func (self Image) At(x, y int) color.Color {    r := (uint8)((float64)(x) / (float64)(self.w) * 255.0)    g := (uint8)((float64)(y) / (float64)(self.h) * 255.0)    b := (uint8)((float64)(x * y) / (float64)(self.w * self.h) * 255.0)    return color.RGBA{r, g, b, 255}}func main() {    m := Image{255, 255}    pic.ShowImage(m)}

等价二叉树

package mainimport (    "fmt"    "golang.org/x/tour/tree")// Walk 步进 tree t 将所有的值从 tree 发送到 channel ch。func Walk(t *tree.Tree, ch chan int) {    if t == nil {        return    }    Walk(t.Left, ch)    ch <- t.Value    Walk(t.Right, ch)}// Same 检测树 t1 和 t2 是否含有相同的值。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 := 0; i < 10; i++ {        x, y := <-ch1, <-ch2        fmt.Println(x, y)        if x != y {            return false        }    }    return true}func main() {    fmt.Println(Same(tree.New(1), tree.New(1)))}

Web 爬虫

package mainimport (    "fmt"    "sync")type Fetcher interface {    // Fetch 返回 URL 的 body 内容，并且将在这个页面上找到的 URL 放到一个 slice 中。    Fetch(url string) (body string, urls []string, err error)}// Crawl 使用 fetcher 从某个 URL 开始递归的爬取页面，直到达到最大深度。func Crawl(url string, depth int, fetcher Fetcher, crawled Crawled, out chan string, end chan bool) {    // TODO: 并行的抓取 URL。    // TODO: 不重复抓取页面。        // 下面并没有实现上面两种情况：    if depth <= 0 {        end <- true        return    }    crawled.mux.Lock()    if _, ok := crawled.crawled[url]; ok {        crawled.mux.Unlock()        end <- true        return    }    crawled.crawled[url] = 1    crawled.mux.Unlock()    _, urls, err := fetcher.Fetch(url)    if err != nil {        fmt.Println(err)        end <- true        return    }    out <- url    //fmt.Println("found: ", url, body)    for _, u := range urls {        go Crawl(u, depth-1, fetcher, crawled, out, end)    }    for i := 0; i < len(urls); i++ {        <-end    }    end <- true    return}type Crawled struct {    crawled map[string]int    mux sync.Mutex}func main() {    crawled := Crawled{make(map[string]int), sync.Mutex{}}    out := make(chan string)    end := make(chan bool)    go Crawl("http://golang.org/", 4, fetcher, crawled, out, end)    for {        select {        case url := <-out:            fmt.Println("found: ", url)        case <-end:            return        }    }}// fakeFetcher 是返回若干结果的 Fetcher。type fakeFetcher map[string]*fakeResulttype 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 是填充后的 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/",        },    },}