159 lines
2.5 KiB
Go
159 lines
2.5 KiB
Go
package main
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import (
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"errors"
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"fmt"
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"sync"
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"time"
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)
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// 常量
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const Pi = 3.14159
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// 结构体
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type Circle struct {
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Radius float64
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}
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// 方法（值接收者）
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func (c Circle) Area() float64 {
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return Pi * c.Radius * c.Radius
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}
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// 方法（指针接收者）
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func (c *Circle) Scale(factor float64) {
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c.Radius *= factor
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}
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// 接口
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type Shape interface {
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Area() float64
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}
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// 函数（多返回值）
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func divide(a, b float64) (float64, error) {
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if b == 0 {
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return 0, errors.New("division by zero")
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}
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return a / b, nil
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}
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func PrintHalloworld() {
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fmt.Println("Hello, World!")
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}
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// 主函数
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func main() {
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// 变量声明
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var a int = 10
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b := 20
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c, d := 30, 40
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fmt.Println("Variables:", a, b, c, d)
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// 数组与切片
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arr := [3]int{1, 2, 3}
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slice := []int{4, 5, 6}
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slice = append(slice, 7)
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fmt.Println("Array:", arr, "Slice:", slice)
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// 映射
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m := map[string]int{"one": 1, "two": 2}
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fmt.Println("Map:", m)
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// 控制结构
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if a > 5 {
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fmt.Println("a is greater than 5")
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} else {
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fmt.Println("a is not greater than 5")
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}
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for i := 0; i < 3; i++ {
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fmt.Println("Loop:", i)
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}
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switch a {
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case 10:
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fmt.Println("a is 10")
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default:
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fmt.Println("a is not 10")
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}
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// 函数调用
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result, err := divide(10, 2)
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if err != nil {
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fmt.Println("Error:", err)
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} else {
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fmt.Println("Division result:", result)
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}
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// 指针
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x := 10
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p := &x
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*p = 20
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fmt.Println("Pointer:", x)
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// 结构体与方法
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circle := Circle{Radius: 5}
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fmt.Println("Circle area:", circle.Area())
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circle.Scale(2)
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fmt.Println("Scaled circle area:", circle.Area())
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// 接口
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var shape Shape = Circle{Radius: 3}
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fmt.Println("Shape area:", shape.Area())
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// 错误处理
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_, err = divide(10, 0)
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if err != nil {
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fmt.Println("Error:", err)
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}
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// 并发
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var wg sync.WaitGroup
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go PrintHalloworld()
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wg.Add(1)
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go func() {
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defer wg.Done()
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fmt.Println("Running in goroutine")
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}()
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wg.Wait()
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// Channel
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ch := make(chan int)
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go func() {
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ch <- 42
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}()
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value := <-ch
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fmt.Println("Channel value:", value)
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// Select
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ch1 := make(chan string)
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ch2 := make(chan string)
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go func() {
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time.Sleep(1 * time.Second)
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ch1 <- "from ch1"
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}()
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go func() {
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time.Sleep(2 * time.Second)
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ch2 <- "from ch2"
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}()
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select {
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case msg := <-ch1:
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go PrintHalloworld()
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fmt.Println("Select:", msg)
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case msg := <-ch2:
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fmt.Println("Select:", msg)
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case <-time.After(3 * time.Second):
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fmt.Println("Timeout")
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}
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// Defer
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defer fmt.Println("Defer: This runs last")
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fmt.Println("Main function end")
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}
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func add(a, b int) (x, y int) {
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x = a + b
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y = a - b
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return
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}
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