go tour 学习笔记

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	b:=1.00
	for z:=1.00;z<math.Trunc(math.Sqrt(2)*math.Pow10(2))/math.Pow10(2);z+=0.01 {
	     b = z - (z*z-x)/(2*z)
	}
   	return b
}

func main() {
	fmt.Println(Sqrt(2))
	fmt.Println(math.Trunc(math.Sqrt(2)*math.Pow10(2))/math.Pow10(2))
        fmt.Println(math.Sqrt(2))
}

package main

import (
	"fmt"
	"runtime"
)

func main() {
	fmt.Print("Go runs on ")
	switch os := runtime.GOOS; os {
	case "darwin":
		fmt.Println("OS X.")
	case "linux":
		fmt.Println("Linux.")
	default:
		// freebsd, openbsd,
		// plan9, windows...
		fmt.Printf("%s.", os)
	}
}

package main
import (
	"golang.org/x/tour/wc"
	"strings"
)

func WordCount(s string) map[string]int {
	m := make(map[string]int)
	for _,value:=  range strings.Fields(s) {
		m[value]+=1
	}
	return m
}

func main() {
	wc.Test(WordCount)
}

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	f_slice := make([]int, 2)
	f_slice = []int{0,1}
	f_index :=0
	return func() int {
		if f_index >1 { 
	    	f_slice = append(f_slice,f_slice[f_index-1]+f_slice[f_index-2])
		}
		f_index +=1
		return f_slice[f_index-1]
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

package main

import "fmt"

type IPAddr [4]byte

// TODO: Add a "String() string" method to IPAddr.
func (m IPAddr) String() string {
	var ret string
	for i, value := range m {
		if i==0 { 
			ret +=fmt.Sprintf("%v",value)
		} else {
			ret += fmt.Sprintf(".%v",value)
		}
	}
	return ret
}

func main() {
	addrs := map[string]IPAddr{
		"loopback":  {127, 0, 0, 1},
		"googleDNS": {8, 8, 8, 8},
	}
	for n, a := range addrs {
		fmt.Printf("%v: %v\n", n, a)
	}
}