go语言程序设计中的一个例子加注释

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// Copyright 漏 2010-12 Qtrac Ltd.

//

// This program or package and any associated files are licensed under the

// Apache License, Version 2.0 (the "License"); you may not use these files

// except in compliance with the License. You can get a copy of the License

// at: http://www.apache.org/licenses/LICENSE-2.0.

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

package main

import (

    "fmt"

    "log"

    "net/http"

    "sort"

    "strconv"

    "strings"

const (

    //以下的常量定义，其实是根据一个html来定义的

    pageTop = `<!DOCTYPE HTML><html><head>

<style>.error{color:#FF0000;}</style></head><title>Statistics</title>

<body><h3>Statistics</h3>

<p>Computes basic statistics for a given list of numbers</p>`

    form = `<form action="/" method="POST">

<label for="numbers">Numbers (comma or space-separated):</label><br />

<input type="text" name="numbers" size="30"><br />

<input type="submit" value="Calculate">

</form>`

    pageBottom = `</body></html>`

    //引用了error定义的风格

    anError = `<p class="error">%s</p>`

type statistics struct {

    numbers []float64

    mean    float64

    median  float64

func main() {

    http.HandleFunc("/", homePage)

    if err := http.ListenAndServe(":9001", nil); err != nil {

        log.Fatal("failed to start server", err)

func homePage(writer http.ResponseWriter, request *http.Request) {

    err := request.ParseForm()        // Must be called before writing response

    fmt.Fprint(writer, pageTop, form) // 行头

    //如果出错，则会在打印出错误信息

    if err != nil {

        fmt.Fprintf(writer, anError, err)

    } else {

        if numbers, message, ok := processRequest(request); ok {

            stats := getStats(numbers)             //取得排序后和计算好的数据

            fmt.Fprint(writer, formatStats(stats)) // 格式化后数据输出

        } else if message != "" {

            fmt.Fprintf(writer, anError, message)

    fmt.Fprint(writer, pageBottom) //行尾

func processRequest(request *http.Request) ([]float64, string, bool) {

    var numbers []float64                                                 //定义成切片

    if slice, found := request.Form["numbers"]; found && len(slice) > 0 { //取得number项

        text := strings.Replace(slice[0], ",", " ", -1) // slice[0] ?

        for _, field := range strings.Fields(text) {

            if x, err := strconv.ParseFloat(field, 64); err != nil { //转换成浮点数

                return numbers, "'" + field + "' is invalid", false

            } else {

                numbers = append(numbers, x) //用内置函数append追加到切片中

    if len(numbers) == 0 {

        return numbers, "", false // no data first time form is shown

    return numbers, "", true

func formatStats(stats statistics) string {

    //格式化输出

    return fmt.Sprintf(`<table border="1">

<tr><th colspan="2">Results</th></tr>

<tr><td>Numbers</td><td>%v</td></tr>

<tr><td>Count</td><td>%d</td></tr>

<tr><td>Mean</td><td>%f</td></tr>

<tr><td>Median</td><td>%f</td></tr>

</table>`, stats.numbers, len(stats.numbers), stats.mean, stats.median)

func getStats(numbers []float64) (stats statistics) {

    stats.numbers = numbers                           // go语言中的 返回值技巧

    sort.Float64s(stats.numbers)                      //排序包

    stats.mean = sum(numbers) / float64(len(numbers)) //平均值时，先转换成float64，不然有可以是整数相除，取整了

    stats.median = median(numbers)

    return stats

func sum(numbers []float64) (total float64) {

    for _, x := range numbers {

        total += x

    return total

func median(numbers []float64) float64 {

    middle := len(numbers) / 2

    result := numbers[middle]

    if len(numbers)%2 == 0 {

        result = (result + numbers[middle-1]) / 2

    return result

go语言程序设计中的一个例子 加注释