go basic

go time and rand:

package main

import (
	"fmt"
	"math/rand"
	"time"
)

func main() {
	rand.Seed(time.Now().Unix())
	fmt.Println("My favorite number is :", rand.Int()%20)
}

get the runtime os:

package main

import (
	"fmt"
	"runtime"
)

func main() {
	fmt.Println("Go runs on")
	switch os := runtime.GOOS; os {
	case "darwin":
		fmt.Println("os x")
	case "linux":
		fmt.Println("Linux.")
	default:
		fmt.Println("windows")
	}
}

slice operator

package main

import (
	"fmt"
	// "reflect"
)

func printSlice(s string, x []int) {
	fmt.Printf("%s len=%d cap=%d %v\n", s, len(x), cap(x), x)
}
func main() {
	var a []int
	printSlice("a", a)

	//append works on nil slice
	a = append(a, 0)
	printSlice("a", a)

	a = append(a, 2, 3, 4)
	printSlice("a", a)

}

wordcount:

package main

import (
	"fmt"
)

func WordCount(s string) map[string]int {
	// c := make(map[string]int)
	c := map[string]int{}
	b := []byte(s)
	for _, v := range b {
		fmt.Println(string(v))
		if cap, ok := c[string(v)]; ok {
			c[string(v)] = 1 + cap
		} else {
			c[string(v)] = 1
		}
	}
	return c
}

func main() {
	a := WordCount("wwwcmome")
	fmt.Println(a)
	b := map[string]int{
		"name": 20,
		"age":  30,
	}
	b["work"] = 100
	if cap, ok := b["name1"]; ok {
		fmt.Println(cap)
	} else {
		fmt.Println("nothing")
	}
	fmt.Println(b)
}

闭包

package main

import "fmt"

func adder() func(int) int {
	sum := 0
	return func(x int) int {
		sum += x
		return sum
	}
}

func main() {
	pos, neg := adder(), adder()
	for i := 0; i < 10; i++ {
		fmt.Println(
			pos(i),
			neg(-2*i),
		)
	}
}

check pointer

package main

import (
	"fmt"
	"math"
)

type Abser interface {
	Abs() float64
}

type MyFloat float64

func (f MyFloat) Abs() float64 {
	if f < 0 {
		return float64(-f)
	}
	return float64(f)
}

type Vertex struct {
	x, y float64
}

func (v *Vertex) Abs() float64 {
	return math.Sqrt(v.x*v.x + v.y*v.y)
}

func main() {
	var a Abser
	f := MyFloat(-math.Sqrt2)
	v := Vertex{3, 4}
	a = f
	a = &v
	fmt.Println(a.Abs())
}

strings.NewReader

package main

import (
	"fmt"
	"io"
	"strings"
)

func main() {
	r := strings.NewReader("hello, Reader")
	b := make([]byte, 8)

	for {
		n, err := r.Read(b)
		fmt.Printf("n=%v err=%v b=%v\n", n, err, b)
		fmt.Printf("b[:n] = %q\n", b[:n])
		if err == io.EOF {
			break
		}
	}
}

use golang regexp

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"regexp"
	// "strings"
	// "reflect"
)

func main() {
	resp, err := http.Get("http://www.163.com/")
	if err != nil {
		fmt.Println("http get error")
	}
	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("http read error")
		return
	}
	// fmt.Println(reflect.TypeOf(body))
	src := string(body)
	re, _ := regexp.Compile("http://[[:word:]]+.[[:word:]]+.com")
	sslice := re.FindAllString(src, 1024)
	for k, v := range removeReplaceSliceContent(sslice) {
		fmt.Printf("%30s \t %5d\n", k, v)
	}
}

func removeReplaceSliceContent(s []string) map[string]int {
	b := map[string]int{}
	for _, v := range s {
		b[v] += 1
	}
	return b
}