ch6: fix code format
chai2010
parent
20a8cf71b9
commit
2420954025
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@ -4,8 +4,8 @@
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下面來寫我們第一個方法的例子，這個例子在package geometry下：
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<u><i>gopl.io/ch6/geometry</i></u>
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```go
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gopl.io/ch6/geometry
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package geometry
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import "math"
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@ -14,15 +14,13 @@ type Point struct{ X, Y float64 }
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// traditional function
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func Distance(p, q Point) float64 {
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return math.Hypot(q.X-p.X, q.Y-p.Y)
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return math.Hypot(q.X-p.X, q.Y-p.Y)
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}
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// same thing, but as a method of the Point type
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func (p Point) Distance(q Point) float64 {
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return math.Hypot(q.X-p.X, q.Y-p.Y)
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return math.Hypot(q.X-p.X, q.Y-p.Y)
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}
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```
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上面的代碼里那個附加的參數p，叫做方法的接收器(receiver)，早期的面向對象語言留下的遺産將調用一個方法稱爲“向一個對象發送消息”。
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@ -6,15 +6,15 @@
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// An IntList is a linked list of integers.
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// A nil *IntList represents the empty list.
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type IntList struct {
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Value int
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Tail *IntList
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Value int
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Tail *IntList
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}
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// Sum returns the sum of the list elements.
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func (list *IntList) Sum() int {
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if list == nil {
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return 0
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}
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return list.Value + list.Tail.Sum()
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if list == nil {
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return 0
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}
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return list.Value + list.Tail.Sum()
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}
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```
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@ -22,8 +22,8 @@ func (list *IntList) Sum() int {
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下面是net/url包里Values類型定義的一部分。
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<u><i>net/url</i></u>
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```go
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net/url
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package url
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// Values maps a string key to a list of values.
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@ -31,22 +31,22 @@ type Values map[string][]string
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// Get returns the first value associated with the given key,
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// or "" if there are none.
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func (v Values) Get(key string) string {
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if vs := v[key]; len(vs) > 0 {
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return vs[0]
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}
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return ""
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if vs := v[key]; len(vs) > 0 {
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return vs[0]
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}
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return ""
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}
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// Add adds the value to key.
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// It appends to any existing values associated with key.
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func (v Values) Add(key, value string) {
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v[key] = append(v[key], value)
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v[key] = append(v[key], value)
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}
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```
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這個定義向外部暴露了一個map的類型的變量，併且提供了一些能夠簡單操作這個map的方法。這個map的value字段是一個string的slice，所以這個Values是一個多維map。客戶端使用這個變量的時候可以使用map固有的一些操作(make，切片，m[key]等等)，也可以使用這里提供的操作方法，或者兩者併用，都是可以的：
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<u><i>gopl.io/ch6/urlvalues</i></u>
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```go
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gopl.io/ch6/urlvalues
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m := url.Values{"lang": {"en"}} // direct construction
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m.Add("item", "1")
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m.Add("item", "2")
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@ -4,8 +4,8 @@
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```go
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func (p *Point) ScaleBy(factor float64) {
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p.X *= factor
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p.Y *= factor
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p.X *= factor
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p.Y *= factor
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}
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```
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@ -27,6 +27,7 @@ r := &Point{1, 2}
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r.ScaleBy(2)
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fmt.Println(*r) // "{2, 4}"
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```
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或者這樣：
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```go
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@ -2,13 +2,15 @@
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來看看ColoredPoint這個類型：
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<u><i>gopl.io/ch6/coloredpoint</i></u>
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```go
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gopl.io/ch6/coloredpoint
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import "image/color"
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type Point struct{ X, Y float64 }
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type ColoredPoint struct {
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Point
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Color color.RGBA
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Point
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Color color.RGBA
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}
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```
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@ -47,11 +49,11 @@ p.Distance(q) // compile error: cannot use q (ColoredPoint) as Point
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```go
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func (p ColoredPoint) Distance(q Point) float64 {
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return p.Point.Distance(q)
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return p.Point.Distance(q)
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}
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func (p *ColoredPoint) ScaleBy(factor float64) {
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p.Point.ScaleBy(factor)
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p.Point.ScaleBy(factor)
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}
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```
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@ -61,8 +63,8 @@ func (p *ColoredPoint) ScaleBy(factor float64) {
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```go
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type ColoredPoint struct {
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*Point
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Color color.RGBA
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*Point
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Color color.RGBA
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}
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p := ColoredPoint{&Point{1, 1}, red}
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@ -77,10 +79,11 @@ fmt.Println(*p.Point, *q.Point) // "{2 2} {2 2}"
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```go
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type ColoredPoint struct {
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Point
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color.RGBA
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Point
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color.RGBA
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}
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```
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然後這種類型的值便會擁有Point和RGBA類型的所有方法，以及直接定義在ColoredPoint中的方法。當編譯器解析一個選擇器到方法時，比如p.ScaleBy，它會首先去找直接定義在這個類型里的ScaleBy方法，然後找被ColoredPoint的內嵌字段們引入的方法，然後去找Point和RGBA的內嵌字段引入的方法，然後一直遞歸向下找。如果選擇器有二義性的話編譯器會報錯，比如你在同一級里有兩個同名的方法。
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方法隻能在命名類型(像Point)或者指向類型的指針上定義，但是多虧了內嵌，有些時候我們給匿名struct類型來定義方法也有了手段。
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@ -89,15 +92,15 @@ type ColoredPoint struct {
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```go
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var (
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mu sync.Mutex // guards mapping
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mapping = make(map[string]string)
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mu sync.Mutex // guards mapping
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mapping = make(map[string]string)
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)
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func Lookup(key string) string {
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mu.Lock()
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v := mapping[key]
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mu.Unlock()
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return v
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mu.Lock()
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v := mapping[key]
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mu.Unlock()
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return v
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}
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```
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@ -105,18 +108,18 @@ func Lookup(key string) string {
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```go
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var cache = struct {
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sync.Mutex
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mapping map[string]string
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sync.Mutex
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mapping map[string]string
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}{
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mapping: make(map[string]string),
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mapping: make(map[string]string),
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}
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func Lookup(key string) string {
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cache.Lock()
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v := cache.mapping[key]
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cache.Unlock()
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return v
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cache.Lock()
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v := cache.mapping[key]
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cache.Unlock()
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return v
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}
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```
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@ -68,15 +68,15 @@ func (p Point) Sub(q Point) Point { return Point{p.X - q.X, p.Y - q.Y} }
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type Path []Point
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func (path Path) TranslateBy(offset Point, add bool) {
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var op func(p, q Point) Point
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if add {
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op = Point.Add
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} else {
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op = Point.Sub
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}
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for i := range path {
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// Call either path[i].Add(offset) or path[i].Sub(offset).
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path[i] = op(path[i], offset)
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}
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var op func(p, q Point) Point
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if add {
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op = Point.Add
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} else {
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op = Point.Sub
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}
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for i := range path {
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// Call either path[i].Add(offset) or path[i].Sub(offset).
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path[i] = op(path[i], offset)
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}
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}
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```
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@ -4,38 +4,38 @@ Go語言里的集合一般會用map[T]bool這種形式來表示，T代表元素
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一個bit數組通常會用一個無符號數或者稱之爲“字”的slice或者來表示，每一個元素的每一位都表示集合里的一個值。當集合的第i位被設置時，我們才説這個集合包含元素i。下面的這個程序展示了一個簡單的bit數組類型，併且實現了三個函數來對這個bit數組來進行操作：
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<u><i>gopl.io/ch6/intset</i></u>
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```go
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gopl.io/ch6/intset
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// An IntSet is a set of small non-negative integers.
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// Its zero value represents the empty set.
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type IntSet struct {
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words []uint64
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words []uint64
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}
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// Has reports whether the set contains the non-negative value x.
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func (s *IntSet) Has(x int) bool {
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word, bit := x/64, uint(x%64)
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return word < len(s.words) && s.words[word]&(1<<bit) != 0
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word, bit := x/64, uint(x%64)
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return word < len(s.words) && s.words[word]&(1<<bit) != 0
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}
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// Add adds the non-negative value x to the set.
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func (s *IntSet) Add(x int) {
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word, bit := x/64, uint(x%64)
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for word >= len(s.words) {
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s.words = append(s.words, 0)
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}
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s.words[word] |= 1 << bit
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word, bit := x/64, uint(x%64)
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for word >= len(s.words) {
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s.words = append(s.words, 0)
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}
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s.words[word] |= 1 << bit
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}
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// UnionWith sets s to the union of s and t.
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func (s *IntSet) UnionWith(t *IntSet) {
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for i, tword := range t.words {
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if i < len(s.words) {
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s.words[i] |= tword
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} else {
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s.words = append(s.words, tword)
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}
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}
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for i, tword := range t.words {
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if i < len(s.words) {
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s.words[i] |= tword
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} else {
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s.words = append(s.words, tword)
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}
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}
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}
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```
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@ -46,23 +46,23 @@ func (s *IntSet) UnionWith(t *IntSet) {
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```go
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// String returns the set as a string of the form "{1 2 3}".
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func (s *IntSet) String() string {
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var buf bytes.Buffer
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buf.WriteByte('{')
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for i, word := range s.words {
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if word == 0 {
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continue
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}
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for j := 0; j < 64; j++ {
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if word&(1<<uint(j)) != 0 {
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if buf.Len() > len("{") {
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buf.WriteByte('}')
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}
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fmt.Fprintf(&buf, "%d", 64*i+j)"}")}}
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}
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}
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}
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buf.WriteByte('}')
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return buf.String()
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var buf bytes.Buffer
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buf.WriteByte('{')
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for i, word := range s.words {
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if word == 0 {
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continue
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}
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for j := 0; j < 64; j++ {
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if word&(1<<uint(j)) != 0 {
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if buf.Len() > len("{") {
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buf.WriteByte('}')
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}
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fmt.Fprintf(&buf, "%d", 64*i+j)"}")}}
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}
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}
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}
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buf.WriteByte('}')
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return buf.String()
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}
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```
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@ -63,9 +63,9 @@ func (c *Counter) Reset() { c.n = 0 }
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```go
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package log
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type Logger struct {
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flags int
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prefix string
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// ...
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flags int
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prefix string
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// ...
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}
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func (l *Logger) Flags() int
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func (l *Logger) SetFlags(flag int)
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