[x/tour] s/Point/Vector/, slice examples
X-Tour-Commit: f06beb3f15c349bcf1705eb0b9ce4f46ab862e7a
This commit is contained in:
Andrew Gerrand
Родитель
8d9dd3f4f0
Коммит
0ac69a73c5
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@ -2,7 +2,7 @@
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TODO
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Expand examples as per existing slides
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Slice examples
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Link to slices blog post
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Pointer examples
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Formatting screen width.
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better if short statement example
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@ -22,7 +22,7 @@ highlight error line
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<link href='http://fonts.googleapis.com/css?family=Droid+Sans&v1' rel='stylesheet' type='text/css'>
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<link href='http://fonts.googleapis.com/css?family=Droid+Sans+Mono&v1' rel='stylesheet' type='text/css'>
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<link rel="stylesheet" href="tour.css" charset="utf-8">
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<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js"></script>
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<script src="jquery.js"></script>
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<script src="tour.js"></script>
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</head>
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@ -32,6 +32,27 @@ highlight error line
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<div id="topnav" class="nav">
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<button id="tocbtn">INDEX</button>
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</div>
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<div class="slide nocode">
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<h2>Installing the tour</h2>
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<p>
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If you don't already have Go installed, follow the installation
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instructions at
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<p>
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<pre>
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http://golang.org/doc/install.html
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</pre>
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To install the interactive tour program, run
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<p>
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<pre>
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goinstall go-tour.googlecode.com/hg/gotour
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</pre>
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This will install the tour to your <code>GOROOT</code>
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(or <code>GOPATH</code>, if you have one set).
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<p>
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To start the tour, type "<code>gotour</code>" at the command line.
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</div>
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<h1>A Tour of Go</h1>
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<ol id="toc"></ol>
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@ -613,13 +634,13 @@ package main
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import "fmt"
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type Point struct {
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type Vertex struct {
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X int
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Y int
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}
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func main() {
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fmt.Println(Point{1, 2})
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fmt.Println(Vertex{1, 2})
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}
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</div>
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</div>
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@ -633,13 +654,13 @@ package main
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import "fmt"
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type Point struct {
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type Vertex struct {
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X int
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Y int
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}
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func main() {
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p := Point{1, 2}
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p := Vertex{1, 2}
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q := &p
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q.X = 1e9
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fmt.Println(p)
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@ -661,15 +682,15 @@ package main
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import "fmt"
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type Point struct {
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type Vertex struct {
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X, Y int
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}
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var (
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p = Point{1, 2} // has type Point
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q = &Point{1, 2} // has type *Point
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r = Point{X: 1} // Y:0 is implicit
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s = Point{} // X:0 and Y:0 are implicit
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p = Vertex{1, 2} // has type Vertex
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q = &Vertex{1, 2} // has type *Vertex
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r = Vertex{X: 1} // Y:0 is implicit
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s = Vertex{} // X:0 and Y:0 are implicit
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)
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func main() {
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@ -691,15 +712,15 @@ package main
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import "fmt"
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type Point struct {
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type Vertex struct {
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Lat, Long float64
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}
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var m map[string]Point
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var m map[string]Vertex
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func main() {
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m = make(map[string]Point)
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m["Bell Labs"] = Point{40.68433, 74.39967}
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m = make(map[string]Vertex)
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m["Bell Labs"] = Vertex{40.68433, 74.39967}
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fmt.Println(m["Bell Labs"])
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}
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</div>
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@ -714,13 +735,13 @@ package main
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import "fmt"
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type Point struct {
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type Vertex struct {
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Lat, Long float64
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}
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var m = map[string]Point{
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"Bell Labs": Point{40.68433, -74.39967},
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"Google": Point{37.42202, -122.08408},
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var m = map[string]Vertex{
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"Bell Labs": Vertex{40.68433, -74.39967},
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"Google": Vertex{37.42202, -122.08408},
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}
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func main() {
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@ -733,31 +754,121 @@ func main() {
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<h2>Slices</h2>
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<p>
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A slice points at an array of values and also includes a length.
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<p>
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<code>[]T</code> is a slice with elements of type <code>T</code>.
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<p>
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Element values can be read and written by index:
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<pre>
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s := []int{12, 24}
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fmt.Print(s[1]) // "24"
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s[0] = 42
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fmt.Print(s[0]) // "48"
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</pre>
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<div>
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package main
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import "fmt"
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type Point struct {
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Lat, Long float64
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func main() {
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primes := []int{2, 3, 5, 7, 11, 13}
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fmt.Println("primes ==", primes)
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for i := 0; i < len(primes); i++ {
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fmt.Printf("primes[%d] == %d\n",
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i, primes[i])
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}
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}
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</div>
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</div>
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var places = []Point{
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Point{40.68433, -74.39967},
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Point{37.42202, -122.08408},
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}
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<div class="slide">
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<h2>Slices</h2>
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<p>
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Slices can be re-sliced, creating a new slice value that points to the
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same array.
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<pre>
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s[lo:hi] // == elements of slice s from [lo, hi)
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</pre>
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<div>
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package main
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var empty []Point
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var five = make([]Point, 5)
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import "fmt"
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func main() {
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fmt.Println("Empty: ", len(empty), empty)
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fmt.Println("Five: ", len(five), five)
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fmt.Println("Places:", len(places), places)
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primes := []int{2, 3, 5, 7, 11, 13}
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fmt.Println("Primes:", primes)
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fmt.Println("primes ==", primes)
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fmt.Println("primes[1:4] ==", primes[1:4])
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// missing low index implies 0
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fmt.Println("primes[:3] ==", primes[:3])
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// missing high index implies len(s)
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fmt.Println("primes[4:] ==", primes[4:])
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}
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</div>
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</div>
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<div class="slide">
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<h2>Slices</h2>
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<p>
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The <code>make</code> function allocates an zeroed array and returns
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a slice that refers to that array:
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<pre>
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a := make([]int, 5) // len(b) == 5
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</pre>
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Slices have length and capacity. A slice's capacity is the largest
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portion its underlying array that it can refer to. Pass a third
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argument to <code>make</code> to specify a capacity:
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<p>
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<pre>
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b := make([]int, 0, 5) // len(b) == 0, cap(b) == 5
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</pre>
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Slices can grown by "re-slicing" (up to their capacity):
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<p>
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<pre>
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b = b[:cap(b)] // len(b) == 5, cap(b) == 5
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b = b[1:] // len(b) == 4, cap(b) == 4
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</pre>
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<div>
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package main
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import "fmt"
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func main() {
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a := make([]int, 5)
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printSlice("a", a)
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b := make([]int, 0, 5)
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printSlice("b", b)
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c := b[:2]
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printSlice("c", c)
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d := c[2:5]
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printSlice("d", d)
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}
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func printSlice(n string, s []int) {
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fmt.Printf("%s = %v len = %d cap = %d\n",
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n, s, len(s), cap(s))
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}
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</div>
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</div>
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<div class="slide">
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<h2>Slices</h2>
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<p>
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The zero value of a slice is <code>nil</code>.
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<p>
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A nil slice has a length and capacity of 0.
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<div>
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package main
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import "fmt"
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func main() {
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var empty []int
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fmt.Println(empty, len(empty), cap(empty))
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if empty == nil {
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fmt.Println("nil!")
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}
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}
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</div>
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</div>
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@ -945,26 +1056,6 @@ func main() {
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</div>
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</div>
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<div class="slide nocode">
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<h2>Installing the tour</h2>
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<p>
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If you don't already have Go installed, follow the installation
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instructions at
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<p>
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<pre>
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http://golang.org/doc/install.html
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</pre>
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To install the interactive tour program, run
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<p>
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<pre>
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goinstall go-tour.googlecode.com/hg/gotour
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</pre>
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This will install the tour to your <code>GOROOT</code>
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(or <code>GOPATH</code>, if you have one set).
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<p>
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To start the tour, type "<code>gotour</code>" at the command line.
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</div>
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<div class="slide">
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<h2>Exercise: Loops and Functions</h2>
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<p>
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@ -1130,16 +1221,16 @@ import (
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"math"
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)
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type Point struct {
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type Vertex struct {
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X, Y float64
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}
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func (p *Point) Abs() float64 {
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func (p *Vertex) Abs() float64 {
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return math.Sqrt(p.X*p.X + p.Y*p.Y)
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}
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func main() {
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p := &Point{3, 4}
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p := &Vertex{3, 4}
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fmt.Println(p.Abs())
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}
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</div>
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@ -1198,12 +1289,12 @@ func main() {
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var (
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a Abser
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f = MyFloat(-math.Sqrt2)
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p = Point{3, 4}
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p = Vertex{3, 4}
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)
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a = f // f, a MyFloat, implements Abser
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a = &p // &p, a *Point, implements Abser
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a = p // p, a Point, does NOT implement Abser
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a = &p // &p, a *Vertex, implements Abser
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a = p // p, a Vertex, does NOT implement Abser
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fmt.Println(a.Abs())
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}
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@ -1227,11 +1318,11 @@ func (f MyFloat) Abs() float64 {
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return float64(f)
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}
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type Point struct {
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type Vertex struct {
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X, Y float64
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}
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func (p *Point) Abs() float64 {
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func (p *Vertex) Abs() float64 {
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return math.Sqrt(p.X*p.X + p.Y*p.Y)
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}
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</div>
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