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< ol class = "chapter" >
< li class = "chapter-item expanded " >
< a href = "../index.html" > Go语言圣经< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../preface-zh.html" > 译者序< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../preface.html" > 前言< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1.html" > < strong aria-hidden = "true" > 1.< / strong > 入门< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-01.html" > < strong aria-hidden = "true" > 1.1.< / strong > Hello, World< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-02.html" > < strong aria-hidden = "true" > 1.2.< / strong > 命令行参数< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-03.html" > < strong aria-hidden = "true" > 1.3.< / strong > 查找重复的行< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-04.html" > < strong aria-hidden = "true" > 1.4.< / strong > GIF动画< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-05.html" > < strong aria-hidden = "true" > 1.5.< / strong > 获取URL< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-06.html" > < strong aria-hidden = "true" > 1.6.< / strong > 并发获取多个URL< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-07.html" > < strong aria-hidden = "true" > 1.7.< / strong > Web服务< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch1/ch1-08.html" > < strong aria-hidden = "true" > 1.8.< / strong > 本章要点< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a >
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< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-02.html" > < strong aria-hidden = "true" > 2.2.< / strong > 声明< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-03.html" > < strong aria-hidden = "true" > 2.3.< / strong > 变量< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-04.html" > < strong aria-hidden = "true" > 2.4.< / strong > 赋值< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-05.html" > < strong aria-hidden = "true" > 2.5.< / strong > 类型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-06.html" > < strong aria-hidden = "true" > 2.6.< / strong > 包和文件< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch2/ch2-07.html" > < strong aria-hidden = "true" > 2.7.< / strong > 作用域< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-01.html" class = "active" > < strong aria-hidden = "true" > 3.1.< / strong > 整型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-02.html" > < strong aria-hidden = "true" > 3.2.< / strong > 浮点数< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-03.html" > < strong aria-hidden = "true" > 3.3.< / strong > 复数< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-04.html" > < strong aria-hidden = "true" > 3.4.< / strong > 布尔型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-05.html" > < strong aria-hidden = "true" > 3.5.< / strong > 字符串< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch3/ch3-06.html" > < strong aria-hidden = "true" > 3.6.< / strong > 常量< / a >
< / li >
< / ol >
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< a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-01.html" > < strong aria-hidden = "true" > 4.1.< / strong > 数组< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-02.html" > < strong aria-hidden = "true" > 4.2.< / strong > Slice< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-03.html" > < strong aria-hidden = "true" > 4.3.< / strong > Map< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-04.html" > < strong aria-hidden = "true" > 4.4.< / strong > 结构体< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-05.html" > < strong aria-hidden = "true" > 4.5.< / strong > JSON< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch4/ch4-06.html" > < strong aria-hidden = "true" > 4.6.< / strong > 文本和HTML模板< / a >
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< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5.html" > < strong aria-hidden = "true" > 5.< / strong > 函数< / a >
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< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-01.html" > < strong aria-hidden = "true" > 5.1.< / strong > 函数声明< / a >
< / li >
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< a href = "../ch5/ch5-02.html" > < strong aria-hidden = "true" > 5.2.< / strong > 递归< / a >
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< a href = "../ch5/ch5-03.html" > < strong aria-hidden = "true" > 5.3.< / strong > 多返回值< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-04.html" > < strong aria-hidden = "true" > 5.4.< / strong > 错误< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-05.html" > < strong aria-hidden = "true" > 5.5.< / strong > 函数值< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-06.html" > < strong aria-hidden = "true" > 5.6.< / strong > 匿名函数< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-07.html" > < strong aria-hidden = "true" > 5.7.< / strong > 可变参数< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-08.html" > < strong aria-hidden = "true" > 5.8.< / strong > Deferred函数< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-09.html" > < strong aria-hidden = "true" > 5.9.< / strong > Panic异常< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch5/ch5-10.html" > < strong aria-hidden = "true" > 5.10.< / strong > Recover捕获异常< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6.html" > < strong aria-hidden = "true" > 6.< / strong > 方法< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-01.html" > < strong aria-hidden = "true" > 6.1.< / strong > 方法声明< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-02.html" > < strong aria-hidden = "true" > 6.2.< / strong > 基于指针对象的方法< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-03.html" > < strong aria-hidden = "true" > 6.3.< / strong > 通过嵌入结构体来扩展类型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-04.html" > < strong aria-hidden = "true" > 6.4.< / strong > 方法值和方法表达式< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-05.html" > < strong aria-hidden = "true" > 6.5.< / strong > 示例: Bit数组< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch6/ch6-06.html" > < strong aria-hidden = "true" > 6.6.< / strong > 封装< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7.html" > < strong aria-hidden = "true" > 7.< / strong > 接口< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-01.html" > < strong aria-hidden = "true" > 7.1.< / strong > 接口是合约< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-02.html" > < strong aria-hidden = "true" > 7.2.< / strong > 接口类型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-03.html" > < strong aria-hidden = "true" > 7.3.< / strong > 实现接口的条件< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-04.html" > < strong aria-hidden = "true" > 7.4.< / strong > flag.Value接口< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-05.html" > < strong aria-hidden = "true" > 7.5.< / strong > 接口值< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-06.html" > < strong aria-hidden = "true" > 7.6.< / strong > sort.Interface接口< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-07.html" > < strong aria-hidden = "true" > 7.7.< / strong > http.Handler接口< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-08.html" > < strong aria-hidden = "true" > 7.8.< / strong > error接口< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-09.html" > < strong aria-hidden = "true" > 7.9.< / strong > 示例: 表达式求值< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-10.html" > < strong aria-hidden = "true" > 7.10.< / strong > 类型断言< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-11.html" > < strong aria-hidden = "true" > 7.11.< / strong > 基于类型断言识别错误类型< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-12.html" > < strong aria-hidden = "true" > 7.12.< / strong > 通过类型断言查询接口< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-13.html" > < strong aria-hidden = "true" > 7.13.< / strong > 类型分支< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-14.html" > < strong aria-hidden = "true" > 7.14.< / strong > 示例: 基于标记的XML解码< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch7/ch7-15.html" > < strong aria-hidden = "true" > 7.15.< / strong > 补充几点< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8.html" > < strong aria-hidden = "true" > 8.< / strong > Goroutines和Channels< / a >
< / li >
< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-01.html" > < strong aria-hidden = "true" > 8.1.< / strong > Goroutines< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-02.html" > < strong aria-hidden = "true" > 8.2.< / strong > 示例: 并发的Clock服务< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-03.html" > < strong aria-hidden = "true" > 8.3.< / strong > 示例: 并发的Echo服务< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-04.html" > < strong aria-hidden = "true" > 8.4.< / strong > Channels< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-05.html" > < strong aria-hidden = "true" > 8.5.< / strong > 并发的循环< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-06.html" > < strong aria-hidden = "true" > 8.6.< / strong > 示例: 并发的Web爬虫< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-07.html" > < strong aria-hidden = "true" > 8.7.< / strong > 基于select的多路复用< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-08.html" > < strong aria-hidden = "true" > 8.8.< / strong > 示例: 并发的目录遍历< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-09.html" > < strong aria-hidden = "true" > 8.9.< / strong > 并发的退出< / a >
< / li >
< li class = "chapter-item expanded " >
< a href = "../ch8/ch8-10.html" > < strong aria-hidden = "true" > 8.10.< / strong > 示例: 聊天服务< / a >
< / li >
< / ol >
< li class = "chapter-item expanded " >
< a href = "../ch9/ch9.html" > < strong aria-hidden = "true" > 9.< / strong > 基于共享变量的并发< / a >
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< ol class = "section" >
< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-01.html" > < strong aria-hidden = "true" > 9.1.< / strong > 竞争条件< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-02.html" > < strong aria-hidden = "true" > 9.2.< / strong > sync.Mutex互斥锁< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-03.html" > < strong aria-hidden = "true" > 9.3.< / strong > sync.RWMutex读写锁< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-04.html" > < strong aria-hidden = "true" > 9.4.< / strong > 内存同步< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-05.html" > < strong aria-hidden = "true" > 9.5.< / strong > sync.Once惰性初始化< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch9/ch9-06.html" > < strong aria-hidden = "true" > 9.6.< / strong > 竞争条件检测< / a >
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< a href = "../ch9/ch9-07.html" > < strong aria-hidden = "true" > 9.7.< / strong > 示例: 并发的非阻塞缓存< / a >
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< a href = "../ch9/ch9-08.html" > < strong aria-hidden = "true" > 9.8.< / strong > Goroutines和线程< / a >
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< / ol >
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< a href = "../ch10/ch10.html" > < strong aria-hidden = "true" > 10.< / strong > 包和工具< / a >
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< a href = "../ch10/ch10-01.html" > < strong aria-hidden = "true" > 10.1.< / strong > 包简介< / a >
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< a href = "../ch10/ch10-02.html" > < strong aria-hidden = "true" > 10.2.< / strong > 导入路径< / a >
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< li class = "chapter-item expanded " >
< a href = "../ch10/ch10-03.html" > < strong aria-hidden = "true" > 10.3.< / strong > 包声明< / a >
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< a href = "../ch10/ch10-04.html" > < strong aria-hidden = "true" > 10.4.< / strong > 导入声明< / a >
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< a href = "../ch10/ch10-05.html" > < strong aria-hidden = "true" > 10.5.< / strong > 包的匿名导入< / a >
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< a href = "../ch10/ch10-06.html" > < strong aria-hidden = "true" > 10.6.< / strong > 包和命名< / a >
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< a href = "../ch10/ch10-07.html" > < strong aria-hidden = "true" > 10.7.< / strong > 工具< / a >
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< a href = "../ch11/ch11.html" > < strong aria-hidden = "true" > 11.< / strong > 测试< / a >
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< a href = "../ch11/ch11-01.html" > < strong aria-hidden = "true" > 11.1.< / strong > go test< / a >
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< a href = "../ch11/ch11-02.html" > < strong aria-hidden = "true" > 11.2.< / strong > 测试函数< / a >
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< a href = "../ch11/ch11-03.html" > < strong aria-hidden = "true" > 11.3.< / strong > 测试覆盖率< / a >
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< a href = "../ch11/ch11-04.html" > < strong aria-hidden = "true" > 11.4.< / strong > 基准测试< / a >
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< a href = "../ch11/ch11-05.html" > < strong aria-hidden = "true" > 11.5.< / strong > 剖析< / a >
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< a href = "../ch11/ch11-06.html" > < strong aria-hidden = "true" > 11.6.< / strong > 示例函数< / a >
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< ul dir = "auto" > < li > < em > 凹语言(Go实现, 面向WASM设计): < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li > < li > < em > WaBook(Go语言实现的MD电子书构建工具): < a href = "https://github.com/wa-lang/wabook" > https://github.com/wa-lang/wabook< / a > < / em > < / li > < / ul > < hr >
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< h2 > 3.1. 整型< / h2 >
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< p > Go语言的数值类型包括几种不同大小的整数、浮点数和复数。每种数值类型都决定了对应的大小范围和是否支持正负符号。让我们先从整数类型开始介绍。< / p >
< p > Go语言同时提供了有符号和无符号类型的整数运算。这里有int8、int16、int32和int64四种截然不同大小的有符号整数类型， ， < / p >
< p > 这里还有两种一般对应特定CPU平台机器字大小的有符号和无符号整数int和uint； ， ， ； < / p >
< p > Unicode字符rune类型是和int32等价的类型， ， < / p >
< p > 最后， ， ， < / p >
< p > 不管它们的具体大小， ， ， ， < / p >
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< p > 其中有符号整数采用2的补码形式表示， ， <!-- raw HTML omitted --> n-1<!-- raw HTML omitted --> 到2<!-- raw HTML omitted --> n-1<!-- raw HTML omitted --> -1。无符号整数的所有bit位都用于表示非负数， <!-- raw HTML omitted --> n<!-- raw HTML omitted --> -1。例如， ， < / p >
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< p > 下面是Go语言中关于算术运算、逻辑运算和比较运算的二元运算符， ： < / p >
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< pre > < code > * / % < < > > & & ^
+ - | ^
== != < < = > > =
& &
||
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< / code > < / pre >
< p > 二元运算符有五种优先级。在同一个优先级，使用左优先结合规则，但是使用括号可以明确优先顺序，使用括号也可以用于提升优先级，例如< code > mask & (1 < < 28)< / code > 。< / p >
< p > 对于上表中前两行的运算符，例如+运算符还有一个与赋值相结合的对应运算符+=，可以用于简化赋值语句。< / p >
< p > 算术运算符< code > +< / code > 、< code > -< / code > 、< code > *< / code > 和< code > /< / code > 可以适用于整数、浮点数和复数，但是取模运算符%仅用于整数间的运算。对于不同编程语言，%取模运算的行为可能并不相同。在Go语言中， < code > -5%3< / code > 和< code > -5%-3< / code > 结果都是-2。除法运算符< code > /< / code > 的行为则依赖于操作数是否全为整数，比如< code > 5.0/4.0< / code > 的结果是1.25， ， < / p >
< p > 一个算术运算的结果， ， ， ， ， ， ： < / p >
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< pre > < code class = "language-Go" > var u uint8 = 255
fmt.Println(u, u+1, u*u) // " 255 0 1"
var i int8 = 127
fmt.Println(i, i+1, i*i) // " 127 -128 1"
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< / code > < / pre >
< p > 两个相同的整数类型可以使用下面的二元比较运算符进行比较；比较表达式的结果是布尔类型。< / p >
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< pre > < code > == 等于
!= 不等于
< 小于
< = 小于等于
> 大于
> = 大于等于
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< / code > < / pre >
< p > 事实上，布尔型、数字类型和字符串等基本类型都是可比较的，也就是说两个相同类型的值可以用==和!=进行比较。此外，整数、浮点数和字符串可以根据比较结果排序。许多其它类型的值可能是不可比较的，因此也就可能是不可排序的。对于我们遇到的每种类型，我们需要保证规则的一致性。< / p >
< p > 这里是一元的加法和减法运算符：< / p >
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< pre > < code > + 一元加法（无效果）
- 负数
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< / code > < / pre >
< p > 对于整数，+x是0+x的简写， ； ， ， < / p >
< p > Go语言还提供了以下的bit位操作运算符， ： < / p >
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< pre > < code > & 位运算 AND
| 位运算 OR
^ 位运算 XOR
& ^ 位清空（ ）
< < 左移
> > 右移
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< / code > < / pre >
< p > 位操作运算符< code > ^< / code > 作为二元运算符时是按位异或（ ） ， ； ， < code > & ^< / code > 用于按位置零（ ） ： ， < code > z = x & ^ y< / code > 结果z的对应的bit位为0， < / p >
< p > 下面的代码演示了如何使用位操作解释uint8类型值的8个独立的bit位。它使用了Printf函数的%b参数打印二进制格式的数字； ， < / p >
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< pre > < code class = "language-Go" > var x uint8 = 1< < 1 | 1< < 5
var y uint8 = 1< < 1 | 1< < 2
fmt.Printf(" %08b\n" , x) // " 00100010" , the set {1, 5}
fmt.Printf(" %08b\n" , y) // " 00000110" , the set {1, 2}
fmt.Printf(" %08b\n" , x& y) // " 00000010" , the intersection {1}
fmt.Printf(" %08b\n" , x|y) // " 00100110" , the union {1, 2, 5}
fmt.Printf(" %08b\n" , x^y) // " 00100100" , the symmetric difference {2, 5}
fmt.Printf(" %08b\n" , x& ^y) // " 00100000" , the difference {5}
for i := uint(0); i < 8; i++ {
if x& (1< < i) != 0 { // membership test
fmt.Println(i) // " 1" , " 5"
}
}
fmt.Printf(" %08b\n" , x< < 1) // " 01000100" , the set {2, 6}
fmt.Printf(" %08b\n" , x> > 1) // " 00010001" , the set {0, 4}
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< / code > < / pre >
< p > （ < / p >
< p > 在< code > x< < n< / code > 和< code > x> > n< / code > 移位运算中， ； ， < code > x< < n< / code > 左移运算等价于乘以$2^n$，一个< code > x> > n< / code > 右移运算等价于除以$2^n$。< / p >
< p > 左移运算用零填充右边空缺的bit位， ， ， ， < / p >
< p > 尽管Go语言提供了无符号数的运算， ， ， ， ， ， < / p >
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< pre > < code class = "language-Go" > medals := []string{" gold" , " silver" , " bronze" }
for i := len(medals) - 1; i > = 0; i-- {
fmt.Println(medals[i]) // " bronze" , " silver" , " gold"
}
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< / code > < / pre >
< p > 另一个选择对于上面的例子来说将是灾难性的。如果len函数返回一个无符号数， ， < code > i > = 0< / code > 则永远为真。在三次迭代之后，也就是< code > i == 0< / code > 时， ， （ ） ， （ ） ， < / p >
< p > 出于这个原因， ， < / p >
< p > 一般来说，需要一个显式的转换将一个值从一种类型转化为另一种类型，并且算术和逻辑运算的二元操作中必须是相同的类型。虽然这偶尔会导致需要很长的表达式，但是它消除了所有和类型相关的问题，而且也使得程序容易理解。< / p >
< p > 在很多场景，会遇到类似下面代码的常见的错误：< / p >
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< pre > < code class = "language-Go" > var apples int32 = 1
var oranges int16 = 2
var compote int = apples + oranges // compile error
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< / code > < / pre >
< p > 当尝试编译这三个语句时，将产生一个错误信息：< / p >
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< pre > < code > invalid operation: apples + oranges (mismatched types int32 and int16)
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< / code > < / pre >
< p > 这种类型不匹配的问题可以有几种不同的方法修复，最常见方法是将它们都显式转型为一个常见类型：< / p >
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< pre > < code class = "language-Go" > var compote = int(apples) + int(oranges)
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< / code > < / pre >
< p > 如2.5节所述， ， ， ； ， ， ： < / p >
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< pre > < code class = "language-Go" > f := 3.141 // a float64
i := int(f)
fmt.Println(f, i) // " 3.141 3"
f = 1.99
fmt.Println(int(f)) // " 1"
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< / code > < / pre >
< p > 浮点数到整数的转换将丢失任何小数部分，然后向数轴零方向截断。你应该避免对可能会超出目标类型表示范围的数值做类型转换，因为截断的行为可能依赖于具体的实现：< / p >
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< pre > < code class = "language-Go" > f := 1e100 // a float64
i := int(f) // 结果依赖于具体实现
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< / code > < / pre >
< p > 任何大小的整数字面值都可以用以0开始的八进制格式书写， ； ， ， < / p >
< p > 当使用fmt包打印一个数值时， ， ： < / p >
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< pre > < code class = "language-Go" > o := 0666
fmt.Printf(" %d %[1]o %#[1]o\n" , o) // " 438 666 0666"
x := int64(0xdeadbeef)
fmt.Printf(" %d %[1]x %#[1]x %#[1]X\n" , x)
// Output:
// 3735928559 deadbeef 0xdeadbeef 0XDEADBEEF
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< / code > < / pre >
< p > 请注意fmt的两个使用技巧。通常Printf格式化字符串包含多个%参数时将会包含对应相同数量的额外操作数，但是%之后的< code > [1]< / code > 副词告诉Printf函数再次使用第一个操作数。第二， < code > #< / code > 副词告诉Printf在用%o、%x或%X输出时生成0、0x或0X前缀。< / p >
< p > 字符面值通过一对单引号直接包含对应字符。最简单的例子是ASCII中类似'a'写法的字符面值， ， < / p >
< p > 字符使用< code > %c< / code > 参数打印，或者是用< code > %q< / code > 参数打印带单引号的字符：< / p >
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< pre > < code class = "language-Go" > ascii := 'a'
unicode := '国'
newline := '\n'
fmt.Printf(" %d %[1]c %[1]q\n" , ascii) // " 97 a 'a'"
fmt.Printf(" %d %[1]c %[1]q\n" , unicode) // " 22269 国 '国'"
fmt.Printf(" %d %[1]q\n" , newline) // " 10 '\n'"
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< / code > < / pre >
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