134 lines
3.0 KiB
Go
134 lines
3.0 KiB
Go
package main
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import (
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"fmt"
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"strconv"
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)
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func main() {
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fmt.Println("=== 变量声明示例 ===")
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// 方式1: 标准声明 可以用于包级别声明
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var name string = "张三"
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var age int = 25
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// 方式2: 类型推断 可以用于包级别声明
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var city = "北京"
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var score = 95.5
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// 方式3: 短声明（最常用） 不能用于包级别声明
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email := "test@example.com"
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isActive := true
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// 方式4: 批量声明
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var (
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username = "admin"
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password = "123456"
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port = 8080
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)
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fmt.Printf("姓名: %s, 年龄: %d, 城市: %s\n", name, age, city)
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fmt.Printf("分数: %.2f, 邮箱: %s, 激活: %t\n", score, email, isActive)
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fmt.Printf("用户: %s, 端口: %d\n", username, port)
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_ = password // 避免未使用变量错误
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fmt.Println("\n=== 数据类型示例 ===")
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// 整数
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var num int = 100
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var byte1 uint8 = 255
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// 浮点数
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var pi float64 = 3.141592653589793
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// 字符串
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var greeting = "Hello, Go!"
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multiline := `
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这是多行字符串
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保留格式
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`
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// 布尔值
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var flag bool = true
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fmt.Printf("整数: %d, 字节: %d\n", num, byte1)
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fmt.Printf("浮点数: %f\n", pi)
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fmt.Printf("字符串: %s\n", greeting)
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fmt.Printf("多行: %s\n", multiline)
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fmt.Printf("布尔: %t\n", flag)
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fmt.Println("\n=== 常量示例 ===")
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const PI = 3.14159
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const AppName = "MyApp"
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const (
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StatusOK = 200
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StatusNotFound = 404
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StatusError = 500
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)
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const (
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Monday = iota // 0
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Tuesday // 1
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Wednesday // 2
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Thursday // 3
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Friday // 4
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)
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fmt.Printf("常量 PI: %f, App: %s\n", PI, AppName)
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fmt.Printf("状态码: %d, %d, %d\n", StatusOK, StatusNotFound, StatusError)
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fmt.Printf("星期: %d, %d, %d\n", Monday, Tuesday, Wednesday)
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fmt.Println("\n=== 类型转换示例 ===")
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// 数值转换
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var i int = 42
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var f float64 = float64(i)
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var u uint = uint(f)
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fmt.Printf("int: %d -> float64: %f -> uint: %d\n", i, f, u)
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// 字符串与数值转换
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num2 := 123
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str := strconv.Itoa(num2)
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fmt.Printf("int to string: %s (类型: %T)\n", str, str)
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str2 := "456"
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num3, err := strconv.Atoi(str2)
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if err != nil {
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fmt.Println("转换失败:", err)
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} else {
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fmt.Printf("string to int: %d (类型: %T)\n", num3, num3)
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}
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fmt.Println("\n=== 运算符示例 ===")
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a, b := 10, 3
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fmt.Printf("%d + %d = %d\n", a, b, a+b)
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fmt.Printf("%d - %d = %d\n", a, b, a-b)
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fmt.Printf("%d * %d = %d\n", a, b, a*b)
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fmt.Printf("%d / %d = %d\n", a, b, a/b)
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fmt.Printf("%d %% %d = %d\n", a, b, a%b)
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// 比较运算
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fmt.Printf("%d == %d: %t\n", a, b, a == b)
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fmt.Printf("%d > %d: %t\n", a, b, a > b)
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// 逻辑运算
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t, f2 := true, false
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fmt.Printf("true && false: %t\n", t && f2)
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fmt.Printf("true || false: %t\n", t || f2)
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fmt.Printf("!true: %t\n", !t)
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fmt.Println("\n=== 零值示例 ===")
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var zeroInt int
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var zeroFloat float64
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var zeroBool bool
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var zeroString string
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fmt.Printf("int零值: %d, float零值: %f, bool零值: %t, string零值: '%s'\n",
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zeroInt, zeroFloat, zeroBool, zeroString)
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}
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