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精校：5.4
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Unknwon
152
eBook/05.4.md
152
eBook/05.4.md
@@ -10,9 +10,9 @@
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for 初始化语句; 条件语句; 修饰语句 {}
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Listing 5.6 [for1.go](examples/chapter_5/for1.go)：
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示例 5.6 [for1.go](examples/chapter_5/for1.go)：
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```
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```go
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package main
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import "fmt"
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@@ -26,13 +26,11 @@ func main() {
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输出：
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```
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This is the 0 iteration
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This is the 1 iteration
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This is the 2 iteration
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This is the 3 iteration
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This is the 4 iteration
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```
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This is the 0 iteration
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This is the 1 iteration
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This is the 2 iteration
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This is the 3 iteration
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This is the 4 iteration
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由花括号括起来的代码块会被重复执行已知次数，该次数是根据计数器（此例为 i）决定的。循环开始前，会执行且仅会执行一次初始化语句 `i := 0;`；这比在循环之前声明更为简短。紧接着的是条件语句 `i < 5;`，在每次循环开始前都会进行判断，一旦判断结果为 false，则退出循环体。最后一部分为修饰语句 `i++`，一般用于增加或减少计数器。
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@@ -44,13 +42,15 @@ This is the 4 iteration
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您还可以在循环中同时使用多个计数器：
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for i, j := 0, N; i < j; i, j = i+1, j-1 {}
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```go
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for i, j := 0, N; i < j; i, j = i+1, j-1 {}
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```
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这得益于 Go 语言具有的平行赋值的特性（可以查看第 7 章 string_reverse.go 中反转数组的示例）。
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您可以将两个 for 循环嵌套起来：
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```
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```go
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for i:=0; i<5; i++ {
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for j:=0; j<10; j++ {
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println(j)
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@@ -60,9 +60,9 @@ for i:=0; i<5; i++ {
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如果您使用 for 循环迭代一个 Unicode 编码的字符串，会发生什么？
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Listing 5.7 [for_string.go](examples/chapter_5/for_string.go)：
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示例 5.7 [for_string.go](examples/chapter_5/for_string.go)：
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```
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```go
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package main
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import "fmt"
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@@ -83,46 +83,44 @@ func main() {
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输出：
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```
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The length of str is: 27
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Character on position 0 is: G
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Character on position 1 is: o
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Character on position 2 is:
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Character on position 3 is: i
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Character on position 4 is: s
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Character on position 5 is:
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Character on position 6 is: a
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Character on position 7 is:
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Character on position 8 is: b
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Character on position 9 is: e
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Character on position 10 is: a
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Character on position 11 is: u
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Character on position 12 is: t
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Character on position 13 is: i
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Character on position 14 is: f
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Character on position 15 is: u
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Character on position 16 is: l
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Character on position 17 is:
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Character on position 18 is: l
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Character on position 19 is: a
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Character on position 20 is: n
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Character on position 21 is: g
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Character on position 22 is: u
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Character on position 23 is: a
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Character on position 24 is: g
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Character on position 25 is: e
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Character on position 26 is: !
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The length of str2 is: 9
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Character on position 0 is: æ
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Character on position 1 is:
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Character on position 2 is: ¥
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Character on position 3 is: æ
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Character on position 4 is:
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Character on position 5 is: ¬
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Character on position 6 is: è
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Character on position 7 is: ª
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Character on position 8 is:
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```
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The length of str is: 27
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Character on position 0 is: G
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Character on position 1 is: o
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Character on position 2 is:
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Character on position 3 is: i
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Character on position 4 is: s
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Character on position 5 is:
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Character on position 6 is: a
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Character on position 7 is:
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Character on position 8 is: b
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Character on position 9 is: e
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Character on position 10 is: a
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Character on position 11 is: u
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Character on position 12 is: t
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Character on position 13 is: i
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Character on position 14 is: f
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Character on position 15 is: u
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Character on position 16 is: l
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Character on position 17 is:
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Character on position 18 is: l
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Character on position 19 is: a
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Character on position 20 is: n
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Character on position 21 is: g
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Character on position 22 is: u
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Character on position 23 is: a
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Character on position 24 is: g
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Character on position 25 is: e
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Character on position 26 is: !
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The length of str2 is: 9
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Character on position 0 is: æ
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Character on position 1 is:
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Character on position 2 is: ¥
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Character on position 3 is: æ
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Character on position 4 is:
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Character on position 5 is: ¬
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Character on position 6 is: è
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Character on position 7 is: ª
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Character on position 8 is:
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如果我们打印 str 和 str2 的长度，会分别得到 27 和 9。
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@@ -139,14 +137,12 @@ Character on position 8 is:
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创建一个程序，要求能够打印类似下面的结果（直到每行 25 个字符时为止）：
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```
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G
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GG
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GGG
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GGGG
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GGGGG
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GGGGGG
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```
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G
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GG
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GGG
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GGGG
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GGGGG
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GGGGGG
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1. 使用 2 层嵌套 for 循环。
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2. 使用一层 for 循环以及字符串截断。
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@@ -171,7 +167,7 @@ for 结构的第二种形式是没有头部的条件判断迭代（类似其它
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Listing 5.8 [for2.go](examples/chapter_5/for2.go)：
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```
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```go
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package main
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import "fmt"
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@@ -188,14 +184,12 @@ func main() {
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输出：
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```
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The variable i is now: 4
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The variable i is now: 3
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The variable i is now: 2
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The variable i is now: 1
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The variable i is now: 0
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The variable i is now: -1
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```
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The variable i is now: 4
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The variable i is now: 3
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The variable i is now: 2
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The variable i is now: 1
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The variable i is now: 0
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The variable i is now: -1
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## 5.4.3 无限循环
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@@ -209,7 +203,7 @@ The variable i is now: -1
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无限循环的经典应用是服务器，用于不断等待和接受新的请求。
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```
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```go
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for t, err = p.Token(); err == nil; t, err = p.Token() {
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...
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}
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@@ -221,7 +215,7 @@ for t, err = p.Token(); err == nil; t, err = p.Token() {
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要注意的是，`val` 始终为集合中对应索引的值拷贝，因此它一般只具有只读性质，对它所做的任何修改都不会影响到集合中原有的值（**译者注：如果 `val` 为指针，则会产生指针的拷贝，依旧可以修改集合中的原值**）。一个字符串是 Unicode 编码的字符（或称之为 `rune`）集合，因此您也可以用它迭代字符串：
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```
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```go
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for pos, char := range str {
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...
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}
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@@ -229,9 +223,9 @@ for pos, char := range str {
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每个 rune 字符和索引在 for-range 循环中是一一对应的。它能够自动根据 UTF-8 规则识别 Unicode 编码的字符。
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Listing 5.9 [range_string.go](examples/chapter_5/range_string.go)：
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示例 5.9 [range_string.go](examples/chapter_5/range_string.go)：
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```
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```go
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package main
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import "fmt"
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@@ -323,7 +317,7 @@ index int(rune) rune char bytes
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**练习 5.9** 以下程序的输出结果是什么？
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```
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```go
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for i := 0; i < 5; i++ {
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var v int
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fmt.Printf("%d ", v)
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@@ -335,7 +329,7 @@ for i := 0; i < 5; i++ {
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1.
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```
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```go
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for i := 0; ; i++ {
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fmt.Println("Value of i is now:", i)
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}
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@@ -343,7 +337,7 @@ for i := 0; ; i++ {
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2.
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```
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```go
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for i := 0; i < 3; {
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fmt.Println("Value of i:", i)
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}
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@@ -351,7 +345,7 @@ for i := 0; i < 3; {
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3.
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```
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```go
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s := ""
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for ; s != "aaaaa"; {
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fmt.Println("Value of s:", s)
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@@ -361,7 +355,7 @@ for ; s != "aaaaa"; {
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4.
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```
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```go
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for i, j, s := 0, 5, "a"; i < 3 && j < 100 && s != "aaaaa"; i, j,
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s = i+1, j+1, s + "a" {
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fmt.Println("Value of i, j, s:", i, j, s)
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