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< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < 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 > < 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 > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a > < / li > < 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 > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-01.html" > < 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 > < / li > < 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 > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-01.html" class = "active" > < 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" > < s
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2022-08-24 10:48:15 +00:00
< li > < em > KusonStack一站式可编程配置技术栈(Go): < a href = "https://github.com/KusionStack/kusion" > https://github.com/KusionStack/kusion< / a > < / em > < / li >
< li > < em > KCL 配置编程语言(Rust): < a href = "https://github.com/KusionStack/KCLVM" > https://github.com/KusionStack/KCLVM< / a > < / em > < / li >
< li > < em > 凹语言™: < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
2022-08-04 06:59:33 +00:00
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< h2 id = "41-数组" > < a class = "header" href = "#41-数组" > 4.1. 数组< / a > < / h2 >
< p > 数组是一个由固定长度的特定类型元素组成的序列， ， （ ） ， ， ， < / p >
< p > 数组的每个元素可以通过索引下标来访问， < / p >
< pre > < code class = "language-Go" > var a [3]int // array of 3 integers
fmt.Println(a[0]) // print the first element
fmt.Println(a[len(a)-1]) // print the last element, a[2]
// Print the indices and elements.
for i, v := range a {
fmt.Printf(" %d %d\n" , i, v)
}
// Print the elements only.
for _, v := range a {
fmt.Printf(" %d\n" , v)
}
< / code > < / pre >
< p > 默认情况下， ， ： < / p >
< pre > < code class = "language-Go" > var q [3]int = [3]int{1, 2, 3}
var r [3]int = [3]int{1, 2}
fmt.Println(r[2]) // " 0"
< / code > < / pre >
< p > 在数组字面值中，如果在数组的长度位置出现的是“...”省略号， ， < / p >
< pre > < code class = "language-Go" > q := [...]int{1, 2, 3}
fmt.Printf(" %T\n" , q) // " [3]int"
< / code > < / pre >
< p > 数组的长度是数组类型的一个组成部分，因此[3]int和[4]int是两种不同的数组类型。数组的长度必须是常量表达式， < / p >
< pre > < code class = "language-Go" > q := [3]int{1, 2, 3}
q = [4]int{1, 2, 3, 4} // compile error: cannot assign [4]int to [3]int
< / code > < / pre >
< p > 我们将会发现， ， ， ： < / p >
< pre > < code class = "language-Go" > type Currency int
const (
USD Currency = iota // 美元
EUR // 欧元
GBP // 英镑
RMB // 人民币
)
symbol := [...]string{USD: " $" , EUR: " €" , GBP: " ￡" , RMB: " ￥" }
fmt.Println(RMB, symbol[RMB]) // " 3 ￥"
< / code > < / pre >
< p > 在这种形式的数组字面值形式中，初始化索引的顺序是无关紧要的，而且没用到的索引可以省略，和前面提到的规则一样，未指定初始值的元素将用零值初始化。例如，< / p >
< pre > < code class = "language-Go" > r := [...]int{99: -1}
< / code > < / pre >
< p > 定义了一个含有100个元素的数组r， ， < / p >
< p > 如果一个数组的元素类型是可以相互比较的，那么数组类型也是可以相互比较的，这时候我们可以直接通过==比较运算符来比较两个数组，只有当两个数组的所有元素都是相等的时候数组才是相等的。不相等比较运算符!=遵循同样的规则。< / p >
< pre > < code class = "language-Go" > a := [2]int{1, 2}
b := [...]int{1, 2}
c := [2]int{1, 3}
fmt.Println(a == b, a == c, b == c) // " true false false"
d := [3]int{1, 2}
fmt.Println(a == d) // compile error: cannot compare [2]int == [3]int
< / code > < / pre >
< p > 作为一个真实的例子， ， ， （ ： ， ） ； ， ： < / p >
< p > < u > < i > gopl.io/ch4/sha256< / i > < / u > < / p >
< pre > < code class = "language-Go" > import " crypto/sha256"
func main() {
c1 := sha256.Sum256([]byte(" x" ))
c2 := sha256.Sum256([]byte(" X" ))
fmt.Printf(" %x\n%x\n%t\n%T\n" , c1, c2, c1 == c2, c1)
// Output:
// 2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881
// 4b68ab3847feda7d6c62c1fbcbeebfa35eab7351ed5e78f4ddadea5df64b8015
// false
// [32]uint8
}
< / code > < / pre >
< p > 上面例子中， ， ， ， ， < / p >
< p > 当调用一个函数的时候， ， ， ， ， ， ， < / p >
< p > 当然，我们可以显式地传入一个数组指针，那样的话函数通过指针对数组的任何修改都可以直接反馈到调用者。下面的函数用于给[32]byte类型的数组清零： < / p >
< pre > < code class = "language-Go" > func zero(ptr *[32]byte) {
for i := range ptr {
ptr[i] = 0
}
}
< / code > < / pre >
< p > 其实数组字面值[32]byte{}就可以生成一个32字节的数组。而且每个数组的元素都是零值初始化， ， ： < / p >
< pre > < code class = "language-Go" > func zero(ptr *[32]byte) {
*ptr = [32]byte{}
}
< / code > < / pre >
< p > 虽然通过指针来传递数组参数是高效的， ， ， ， ， ， ； ， < / p >
< p > < strong > 练习 4.1： < / strong > 编写一个函数， （ < / p >
< p > < strong > 练习 4.2： < / strong > 编写一个程序， ， ， < / p >
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