Detailed explanation of predefined identifiers in Go language-Golang-php.cn

Detailed explanation of predefined identifiers in Go language

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Release： 2024-04-08 10:21:01

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Predefined identifiers are special identifiers in the Go language, used to predefine behaviors such as data types, keywords, and built-in functions. Some common predefined identifiers include the Boolean truth values true and false values false, the floating point types float32 and float64, the integer types int and uint, and the keywords break, for, if, and return.

Detailed explanation of predefined identifiers in Go language

Detailed explanation of Go language predefined identifiers

What are predefined identifiers?

Predefined identifiers are special identifiers defined in the Go language, and they have special meanings. They are used to predefine certain behaviors of the Go language, such as data types, keywords, and built-in functions.

List of predefined identifiers

The following are some of the most common predefined identifiers defined in the Go language standard library:

Constant type identifier

const (
    iota  // 初始化常量序列
    true  // 布尔真值
    false // 布尔假值
    nil   // 空指针
)

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Data type identifier

type (
    bool        // 布尔类型
    byte        // 8 位无符号整数
    complex64   // 复数类型（64 位）
    complex128  // 复数类型（128 位）
    error       // 错误类型
    float32     // 32 位浮点数
    float64     // 64 位浮点数
    int          // 整数类型（取决于平台）
    int8         // 8 位有符号整数
    int16        // 16 位有符号整数
    int32        // 32 位有符号整数
    int64        // 64 位有符号整数
    rune        // UTF-32 编码点类型
    string       // 字符串类型
    uint         // 整数类型（取决于平台）
    uint8        // 8 位无符号整数
    uint16       // 16 位无符号整数
    uint32       // 32 位无符号整数
    uint64       // 64 位无符号整数
    uintptr      // 无符号整数，通常是平台指针大小
)

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Keyword

const (
    break           // 跳出循环或 switch 语句
    case            // switch 语句中的 case 标签
    chan            // 通道类型
    const           // 常量声明
    continue        // 继续循环
    default         // switch 语句中的 default 标签
    defer            // 延迟执行函数
    else            // if 语句中的 else 分支
    fallthrough      // switch 语句中的 fallthrough 语句
    for             // for 循环
    func            // 函数声明
    go              // 启动协程
    goto            // 跳到指定标签
    if              // if 语句
    import          // 导入包
    interface       // 接口类型
    map             // 映射类型
    package         // 包声明
    range           // 范围遍历
    return          // 从函数返回
    select          // 选择通道通信
    struct          // 结构体类型
    switch          // switch 语句
    type            // 类型声明
    var             // 变量声明
)

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Built-in Function

append        // 将元素添加到切片或映射
cap           // 返回切片的容量
close         // 关闭通道
copy          // 复制元素
delete        // 从映射中删除元素
len           // 返回集合的长度
make          // 创建集合
new           // 创建分配内存的新对象
panic         // 终止程序并打印错误消息
print         // 打印值
println       // 打印值并换行
recover       // 处理 panic 并返回错误消息
sort          // 对切片进行排序

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Practical case

In the following code example, we show how to use the predefined identifier iota to create a Group constants:

const (
    Monday    = iota
    Tuesday
    Wednesday
    Thursday
    Friday
    Saturday
    Sunday
)

// ...

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In the above example, iota is used to initialize the Monday constant and then automatically increments with each subsequent constant declaration. This allows us to easily create a set of related constants using a simple syntax.

Using predefined identifiers helps you write cleaner, more readable Go code and ensures consistent naming and behavior.

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