\hGo編程語(yǔ)言指南。本指南涵蓋了該語(yǔ)言的大部分重要特性，主要包Go流程控制語(yǔ)句：for、if、else和復(fù)雜類型：struct、slice和學(xué)習(xí)如何基于已有類型定義新的類型：本課涵蓋了結(jié)構(gòu)體、數(shù)組、slice作為語(yǔ)言的核心部分，Gogorouteinchannel，以及如何使用它們來(lái)實(shí)現(xiàn)不同的并發(fā)Go將并發(fā)作為語(yǔ)言的核心構(gòu)成。本課將對(duì)其進(jìn)行介紹，并提供了一些示例來(lái)Go程序都是由包組成的。\hpackagepackageimportfuncmain()fmt.Println("Myfavoritenumberis",packagepackageimportfuncmain()fmt.Printf("Nowyouhave%gproblems.",math.Nextafter(2,導(dǎo)??Go中，首字母大寫(xiě)的名稱是被導(dǎo)出的。packagepackageimport(funcmain(){（參考\hGo語(yǔ)法定義的文章了解類型以這種形式出現(xiàn)的原因。packagepackageimportfuncadd(xint,yint)intreturnx+funcmain(){fmt.Println(add(42,13))Xint,y x,yx,yintx,ypackagepackageimportfuncadd(x,yint)intreturnx+funcmain(){fmt.Println(add(42,13))mutiple-packagepackageimportfuncswap(x,ystring)(string,string)returny,funcmain()a,b:=swap("hello","world")fmt.Println(a,b)Gopackagepackageimportfuncsplit(sumint)(x,yint){x=sum*4/9y=sum-funcmain(){packagepackageimportvarc,python,javafuncmain()varifmt.Println(i,c,python,packagepackageimportvari,jint=1,funcmain()varc,python,java=true,false,"no!"fmt.Println(i,j,c,python,java)packagepackageimportfuncmain()vari,jint=1,2k:=3c,python,java:=true,false,fmt.Println(i,j,k,c,python,Gointint8int16int32uintuint8uint16uint32uint64uintptrbyte//uint8的別名runeint32Unicodefloat32float64complex64complex128packagepackageimportvar MaxIntuint64==1<<64- complex128=cmplx.Sqrt(-5+funcmain()constf="%T(%v)\n"fmt.Printf(f,ToBe,ToBe)fmt.Printf(fmt.Printf(f,MaxInt,MaxInt)fmt.Printf(f,z,z)數(shù)值類型為布爾類型為packagepackageimportfuncmain()varivarffloat64varbboolvarsstringfmt.Printf("%v%v%v%q\n",i,f,b,CGo的在不同類型之間的項(xiàng)目賦值時(shí)需要顯式轉(zhuǎn)換。試著移除例float64int的轉(zhuǎn)換看看會(huì)發(fā)生什么。packagepackageimportfuncmain()varx,yint=3,varffloat64=math.Sqrt(float64(x*x+varzint=int(f)fmt.Println(x,y,z)varvarivpackagepackageimportfuncmain()v:=42//changeme!fmt.Printf("visoftype%T\n",v)packagepackagemainimport"fmt"constPi=3.14funcmain()constWorld="世界"fmt.Println("Hello",World)fmt.Println("Happy"Pi"Day")constTruth=fmt.Println("Gorules?",packagepackageimportconst =1<<Small=Big>>funcneedInt(xint)int{returnx*10+1funcneedFloat(xfloat64)float64returnx*funcmain(){Go只有一種循環(huán)結(jié)構(gòu)——`for`Java中做的一樣，而`{}`packagepackageimportfuncmain(){sum:=0fori:=0;i<10;i++{sum+=iCJavafor-packagepackageimportfuncmain(){sum:=1for;sum<1000;{sum+=sumfor是Go的基于此可以省略分號(hào)：CwhileGo中叫做`for`packagepackageimportfuncmain(){sum:=1forsum<1000{sum+=sumpackagepackagefuncmain()forif語(yǔ)句除了沒(méi)有了`()`之外（甚至強(qiáng)制不能使用它們），C（耳熟嗎packagepackageimportfuncsqrt(xfloat64)stringifx<0returnsqrt(-x)+returnfuncmain(){fmt.Println(sqrt(2),sqrt(-4))packagepackageimportimportfuncpow(x,n,limfloat64)float64ifv:=math.Pow(x,n);v<limreturnreturnfuncmain(){pow(3,2,pow(3,3,ifpackagepackageimportfuncpow(x,n,limfloat64)float64ifv:=math.Pow(x,n);v<limreturn}elsefmt.Printf("%g>=%g\n",v,vreturnfuncfuncmain(){pow(3,2,pow(3,3,z常?。‐hmath.Sqrt接近嗎？packagepackageimportfuncSqrt(xfloat64)float64funcmain(){packagepackageimportfuncmain(){fmt.Print("Gorunson")switchos:=runtime.GOOS;oscase"darwin":fmt.Println("OSX.")case"linux"://freebsd,//plan9,windows...fmt.Printf("%s.",os)switch（switchswitchi{case0:casef():i==0`f`。注意：Goplayground2009-11-1023:00:00UTCpackagepackageimportfuncmain()fmt.Println("When'sSaturday?")today:=time.Now().Weekday()switchtime.Saturday{casetoday+0:casetoday+1:casetoday+2:fmt.Println("Intwodays.")fmt.Println("Toofarswitch`switchtrue`if-then-elsepackagepackageimportfuncmain()t:=t:=switchcaset.Hour()<12:fmt.Println("Goodmorning!")caset.Hour()<17:fmt.Println("Goodafternoon.")fmt.Println("Gooddeferpackagepackageimportfuncmain()defer閱讀\h博文了解更多關(guān)于deferpackagepackageimportfuncfuncmain()fori:=0;i<10;i++deferGo類型*TT`nil`varp &ii:=p=fmt.Println(*pfmt.Println(*pp*p=通過(guò)指針p設(shè)置與C不同，Go沒(méi)有指針運(yùn)算。packagepackageimportfuncmain()i,j:=42,p:=//pointtofmt.Println(*p)//readithroughthe*p=21 //setithroughthepointerfmt.Println(i)//seethenewvalueofip=p= //pointto*p=*p/37 //dividejthroughthepointerfmt.Println(j)//seethenewvalueofjpackagepackageimporttypeVertexstructXintYfuncmain(){fmt.Println(Vertex{1,2})struct-packagepackageimporttypeVertexstructXintYfuncfuncmain()v:=Vertex{1,v.X=struct-packagepackageimporttypeVertexstructXintYfuncmain()v:=Vertex{1,2}p:=&vp.X=struct-packagepackageimporttypeVertexstruct{X,Yintvarv1=Vertex{1,2}//類型為Vertexv2=Vertex{X:1}//Y:0被省略v3=Vertex{} //X:0和Y:0p=&Vertex{12funcmain(){fmt.Println(v1,p,v2,v3)vara a約，但是請(qǐng)不要擔(dān)心；Go提供了更加便利的方式來(lái)使用數(shù)組。packagepackageimportfuncmain()vara[2]stringa[0]="Hello"a[1]=fmt.Println(a[fmt.Println(a[0],a[1])slice[]TTslicepackagepackageimportfuncmain()p:=[]int{2,3,5,7,11,fmt.Println("p==",fori:=0;i<len(p);i++{fmt.Printf("p[%d]==%d\n",i,p[i])sliceslice值指向相同的數(shù)組。 lohi-1slice slicing-packagepackageimportfuncmain()p:=[]int{2,3,5,7,11,fmt.Println("p==",p)fmt.Println("p[1:4]==",p[1:4])0fmt.Println("p[:3]==",len(s)fmt.Println("p[4:]==",構(gòu)造slicemakeslice指向a:=make([]int,5)// 為了指定容量，可傳遞第三個(gè)參數(shù)到bb:=make([]int,0,5)//len(b)=0,b=b[:cap(b)]//len(b)=5,b= //len(b)=4,packagepackageimportfuncmain()a:=make([]int,5)printSlice("a",a)bb:=make([]int,0,5)printSlice("b",b)c:=printSlice("c",c)d:=c[2:5]printSlice("d",funcprintSlice(sstring,x[]int){fmt.Printf("%slen=%dcap=%d%v\n",s,len(x),cap(x),slice`nil`nilslice0nil-packagepackageimportfuncmain()varzfmt.Println(z,len(z),ifz==nil{向slice添加元素sliceGo`append`\h文檔appendfuncappend(s[]T,vs...T) appendsTT的值將會(huì)添加到slice。appendsliceslices的slice會(huì)指向這個(gè)新分配的數(shù)組。（slice\hslice：使用和內(nèi)幕。packagepackageimportfuncmain()vara[]intprintSlice("a",a)//appendworksonnilslices.a=append(a,0)printSlice("a",a)//theslicegrowsasneeded.a=append(a,1)printSlice("a",a)//wecanaddmorethanoneelementatatime.a=append(a,2,3,4)printSlice("a",funcprintSlice(sstring,x[]int){fmt.Printf("%slen=%dcap=%d%v\n",s,len(x),cap(x),forrangeslicemappackagepackageimportvarpow=[]int{1,2,4,8,16,32,64,funcmain()fori,v:=rangepow{fmt.Printf("2**%d=%d\n",i,v)如果只需要索引值，去掉value”packagepackageimportfuncmain()pow:=make([]int,fori:=rangepow{pow[i]=1<<uint(i)for_,value:=rangepow{fmt.Printf("%d\n",value)實(shí)現(xiàn)`Pic`。它返回一個(gè)slice的長(zhǎng)度`dy`，和slice中每個(gè)元素的長(zhǎng)度的8`dx`。當(dāng)執(zhí)行這個(gè)程序，它會(huì)將整數(shù)轉(zhuǎn)換為灰度（好吧，藍(lán)度）圖片的實(shí)現(xiàn)已經(jīng)完成?？赡苡玫降暮瘮?shù)包括(x+y)/2x*y`x^y`（\h（需要使用循環(huán)來(lái)分配[][]uint8`[]uint8`。packagepackageimport"/p/go-funcPic(dx,dyint)[][]uint8funcmain(){mapmapmakenewnilmap是空packagepackageimporttypetypeVertexstruct{Lat,Longvarmmap[string]Vertexfuncmain(){m=make(map[string]Vertex)m["BellLabs"]=Vertex{40.68433,-fmt.Println(m["Bellmap的文法mappackagepackageimporttypeVertexstruct{Lat,Longfloat64varm=map[string]Vertex{"BellLabs":Vertex{40.68433,-"Google":Vertex{37.42202,-122.08408,funcmain(){的文法packagepackageimporttypeVertexstruct{Lat,Longfloat64varm="BellLabs":{40.68433,- {37.42202,-funcmain(){修改mapmm[key]= elem= delete(m, elem,ok= keym中，`ok`trueok`false`elemmapmap的元素類型的零packagepackageimportfuncmain()m:=m["Answer"]=fmt.Println("Thevalue:",m["Answer"]=fmt.Println("Thevalue:",delete(m,fmt.Println("Thevalue:",v,ok:=fmt.Println("Thevalue:",v,"Present?",`WordCount`s“詞”map\hstrings.Fieldspackagepackageimport"/p/go-funcWordCount(sstring)map[string]intreturnmap[string]int{"x":funcmain(){packagepackageimportfuncmain()hypot:=func(x,yfloat64)float64returnmath.Sqrt(x*x+fmt.Println(hypot(3,Go函數(shù)可以是閉包的。閉包是一個(gè)函數(shù)值，它來(lái)自函數(shù)體的外部的變量引“綁定”在這packagepackageimportfuncadder()func(int)int{sum:=0returnfunc(xint)int{sum+=xreturnfuncmain()pos,neg:=adder(),fori:=0;i<10;i++{packagepackageimportfibonacciintfuncfibonacci()func()intfuncmain()f:=f:=fori:=0;i<10;i++{GopackagepackageimporttypeVertexstruct{X,Yfloat64func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+funcmain()v:=&Vertex{3,4}packagepackageimporttypeMyFloatfunc(fMyFloat)Abs()float64iff<0returnfloat64(-returnfuncmain()f:=MyFloat(-math.Sqrt2)MyFloatAbsScaleVertex代替*Vertex作為接收vVertexScale方法沒(méi)有任何作用。`Scale``v`vAbs`v`。所以讀取的是原始值（通packagepackageimporttypeVertexstruct{X,Yfloat64func(v*Vertex)Scale(ffloat64)v.X=v.X*v.Y=v.Y*func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+funcmain()v:=&Vertex{3,4}fmt.Println(v,v.Abs())注意：例子代碼的加粗標(biāo)紅Abs只定義在（指針類型）Vertex（值類型）`Abser`packageimporttypeAbserinterface{Abs()float64funcmain()varaf:=MyFloat(-math.Sqrt2)v:=Vertex{3,4}a=f//aMyFloat實(shí)現(xiàn)了Absera&va*Vertex實(shí)現(xiàn)了下面一行，vVertex（AbsertypeMyFloatfunc(fMyFloat)Abs()float64iff<0returnfloat64(-returntypeVertexstruct{X,Yfloat64func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+\hioReader`Writer`packagepackageimporttypeReaderinterfaceRead(b[]byte)(nint,errtypeWriterinterfaceWrite(b[]byte)(nint,errtypeReadWriterinterface{funcmain()varwos.StdoutWriterw=os.Stdoutfmt.Fprintf(w,"hello,\h\htypetypeStringerinterface{String()stringStringer是一個(gè)可以用字符串描述自己的類型。`fmt`（還有許多其他packagepackageimporttypePersonstruct{NamestringAgefunc(pPerson)String()stringreturnfmt.Sprintf("%v(%vyears)",p.Name,funcmain()a:=Person{"ArthurDent",z:=Person{"ZaphodBeeblebrox",9001}fmt.Println(a,z)例如，`IPAddr{1,`2,`3,`4}`應(yīng)當(dāng)輸出`""`。packagepackageimporttypeIPAddr//TODO:Adda"String()string"methodtofuncmain()addrs:=map[string]IPAddr{"loopback":{127,0,0,1},"googleDNS":{8,8,8,forn,a:=rangeaddrs{fmt.Printf("%v:%v\n",n,a)Goerrorfmt.Stringer類似，`error`typetypeerrorinterface{Error()string（fmt.Stringer類似，`fmt``error`。`nil`i,i,err:=strconv.Atoi("42")iferr!=nil{fmt.Printf("couldn'tconvertnumber:%v\n",fmt.Println("Convertedinteger:",errornilnilerrorpackagepackageimporttypeMyErrorstruct{Whentime.TimeWhatstringfunc(e*MyError)Error()stringreturnfmt.Sprintf("at%v,%s",e.When,e.What)funcrun()errorreturn&MyError{"itdidn'tfuncmain()iferr:=run();err!=nil{Sqrtnil的錯(cuò)誤值。復(fù)數(shù)同樣也不被支typetypeErrNegativeSqrtfuncfunc(eErrNegativeSqrt)Error()`error`ErrNegativeSqrt(-`"cannotSqrtnegativenumber:2"`packagepackageimportfuncSqrt(xfloat64)(float64,error)return0,funcmain(){ioio.ReaderGo標(biāo)準(zhǔn)庫(kù)包含了這個(gè)接口的\h許多實(shí)現(xiàn)func(T)Read(b[]byte)(nint,err Readslice\hstrings.Reader8字節(jié)的速度讀取它packagepackageimportfuncmain()r:=strings.NewReader("Hello,b:=make([]byte,forn,err:=fmt.Printf("n=%verr=%vb=%v\n",n,err,b)fmt.Printf("b[:n]=%q\n",b[:n])iferr==io.EOFReaderASCII字符'A'packagepackageimport"/p/go-typeMyReader//TODO:AddaRead([]byte)(int,error)methodtofuncmain(){\hio.Reader`io.Reader`，然后通過(guò)某種形式修改數(shù)例如，\hgzip.NewReader`io.Reader`（壓縮的數(shù)據(jù)流）并且返回同樣io.Reader的`*gzip.Reader`（解壓縮后的數(shù)據(jù)流）。io.Reader`rot13Reader`io.Reader\hrot13Read`io.Reader`packagepackageimport(typerot13Readerstruct{rio.Readerfuncmain()ss:=strings.NewReader("Lbhpenpxrqgurpbqr!")r:=rot13Reader{s}io.Copy(os.Stdout,服務(wù)器\hhttphttp.HandlerHTTPpackagepackagetypeHandlerinterfaceServeHTTP(wResponseWriter,rHello`http.Handler`。\hhttp://localhost:4000/會(huì)看到來(lái)自程序的問(wèn)候。web的指南用戶界面運(yùn)行。為了嘗試編寫(xiě)服務(wù)器，可能需要\hGoweb-packagepackageimporttypeHellofunc(hHello)ServeHTTP(whttp.ResponseWriter,r*http.Request){fmt.Fprint(w,"Hello!")funcmain()varherr:=http.ListenAndServe(err:=http.ListenAndServe("localhost:4000",iferr!=nil{處理ServeHTTPweb服務(wù)器中注冊(cè)它typetypeStringtypeStructstruct{Greetingstring http.Handle("/string",String("I'mafrayedknot."))http.Handle("/struct",http.Handle("/string",String("I'mafrayedknot."))http.Handle("/struct",&Struct{"Hello",":","Gophers!"})webweb服務(wù)，你可能需要\h安裝Go。packagepackageimportfuncmain()//yourhttp.Handlecallsherelog.Fatal(http.ListenAndServe("localhost:4000",nil))\hPackageimageImagepackagepackagetypeImageinterface{ColorModel()color.ModelBounds()RectangleAt(x,yint)*注意*：`Bounds`Rectangle\himage.Rectangleimage（參閱\h文檔了解全部信息。\himage/color包packagepackageimportfuncmain()m:=image.NewRGBA(image.Rect(0,0,100,100))fmt.Println(m.At(0,image.ImagesliceImage類型，要實(shí)現(xiàn)\h必要的方法`pic.ShowImage`Bounds`image.Rectangle``image.Rect(0,0w,h)`ColorModel`color.RGBAModel``color.RGBA{v,v,255,255}`packagepackageimport"/p/go-typeImagestruct{}funcmain(){m:=Image{}goroutineGogogof(x,y,goroutinef(x,f(x,y,fxyzgoroutinegoroutine`f`goroutine在相同的地址空間中運(yùn)行，因此訪問(wèn)共享內(nèi)存必須進(jìn)行同步。\hGo中并不經(jīng)常用到，因?yàn)橛衅渌霓k法。（在接下packagepackageimportfuncsay(sstring)fori:=0;i<5;i++{time.Sleep(100*time.Millisecond)funcmain()gosay("world")channelchannel操作符<-chch vchannelchvchchvmapslice一樣，channelch:=make(chan packagepackageimportfuncsum(a[]int,cchanint){sum:=0for_,v:=rangea{sum+=vcsum將和送入funcmain()a:=[]int{7,2,8,-9,4,c:=make(changosum(a[:len(a)/2],gosum(a[len(a)/2:],xyc,<-ccfmt.Println(x,y,緩沖channel_帶緩沖的_make提供第二個(gè)參數(shù)作為緩沖長(zhǎng)度來(lái)初始化一個(gè)緩沖channel：ch:=make(chanint, channel發(fā)送數(shù)據(jù)的時(shí)候，只有在緩沖區(qū)滿的時(shí)候才會(huì)阻塞。當(dāng)緩沖區(qū)buffered-packagepackageimportfuncmain()c:=make(chanint,2)c<-1c<-range和closechannel來(lái)表示再?zèng)]有值會(huì)被發(fā)送了。接收者可以通過(guò)賦值語(yǔ)句的第二參數(shù)來(lái)測(cè)試channel是否被關(guān)閉：當(dāng)沒(méi)有值可以接收并且channelv,ok:=<- ok`false``forirangec`channel注意：只有發(fā)送者才能關(guān)閉channel，而不是接收者。向一個(gè)已經(jīng)關(guān)閉的channelpanic。還要注意：channel與文件不同；通常情況關(guān)閉，例如中斷一個(gè)`range`。packagepackageimportfuncfibonacci(nint,cchanint){x,y:=0,1fori:=0;i<n;i++{c<-xx,y=y,funcmain()c:=make(chanint,10)gofibonacci(cap(c),c)fori:=rangec{selectgoroutinepackagepackageimportfuncfuncfibonacci(c,quitchanint){x,y:=0,1forselectcasec<-x,y=y,case<-quit:funcmain()c:=make(chanint)quit:=make(chanint)gofunc(){fori:=0;i<10;i++{quit<-fibonacci(c,select中的其他條件分支都沒(méi)有準(zhǔn)備好的時(shí)候，`default`selectselectcasei:=<-i從cpackagepackageimportfuncmain()tick:=time.Tick(100*time.Millisecond)boom:=time.After(500*time.Millisecond)for{selectcase<-tick:case<-boom: time.Sleep(50*time.Millisecond)叉樹(shù)保存了序列