Hello World

这里展示了一个示例 go 程序。

package main

import "fmt"

func main() {
  message := greetMe("world")
  fmt.Println(message)
}

func greetMe(name string) string {
  return "Hello, " + name + "!"
}

运行程序如下：

$ go run hello.go
变量

正常声明：

var msg string
msg = "Hello"

捷径：

msg := "Hello"
常量
const Phi = 1.618
字符串
str := "Hello"

多行字符串

str := `Multiline
string`
Numbers

典型类型

num := 3          // int
num := 3.         // float64
num := 3 + 4i     // complex128
num := byte('a')  // byte (alias for uint8)

其他类型

var u uint = 7        // uint (unsigned)
var p float32 = 22.7  // 32-bit float
数组
// var numbers [5]int
numbers := [...]int{0, 0, 0, 0, 0}
指针
func main () {
  b := *getPointer()
  fmt.Println("Value is", b)

func getPointer () (myPointer *int) {
  a := 234
  return &a

a := new(int)
*a = 234

指针指向变量的内存位置。Go 是完全垃圾收集的。

类型转换
i := 2
f := float64(i)
u := uint(i)
切片
slice := []int{2, 3, 4}

slice := []byte("Hello")
条件
if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}

if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")
切换
switch day {
  case "sunday":
    // cases don't "fall through" by default!
    fallthrough

  case "saturday":
    rest()

  default:
    work()
}
循环
for count := 0; count <= 10; count++ {
  fmt.Println("My counter is at", count)
}

entry := []string{"Jack","John","Jones"}
for i, val := range entry {
  fmt.Printf("At position %d, the character %s is present\n", i, val)

n := 0
x := 42
for n != x {
  n := guess()
}
条件
if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}

if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")
变量
NAME="John"
echo $NAME
echo "$NAME"
echo "${NAME}
条件
if [[ -z "$string" ]]; then
  echo "String is empty"
elif [[ -n "$string" ]]; then
  echo "String is not empty"
fi