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90 lines
2.0 KiB
Markdown
90 lines
2.0 KiB
Markdown
# 7.4 切片重组（reslice）
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我们已经知道切片创建的时候通常比相关数组小，例如：
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```go
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slice1 := make([]type, start_length, capacity)
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```
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其中 `start_length` 作为切片初始长度而 `capacity` 作为相关数组的长度。
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这么做的好处是我们的切片在达到容量上限后可以扩容。改变切片长度的过程称之为切片重组 **reslicing**，做法如下：`slice1 = slice1[0:end]`，其中 end 是新的末尾索引（即长度）。
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将切片扩展 1 位可以这么做：
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```go
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sl = sl[0:len(sl)+1]
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```
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切片可以反复扩展直到占据整个相关数组。
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示例 7.11 [reslicing.go](examples/chapter_7/reslicing.go)
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```go
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package main
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import "fmt"
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func main() {
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slice1 := make([]int, 0, 10)
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// load the slice, cap(slice1) is 10:
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for i := 0; i < cap(slice1); i++ {
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slice1 = slice1[0:i+1]
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slice1[i] = i
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fmt.Printf("The length of slice is %d\n", len(slice1))
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}
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// print the slice:
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for i := 0; i < len(slice1); i++ {
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fmt.Printf("Slice at %d is %d\n", i, slice1[i])
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}
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}
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```
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输出结果：
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The length of slice is 1
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The length of slice is 2
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The length of slice is 3
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The length of slice is 4
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The length of slice is 5
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The length of slice is 6
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The length of slice is 7
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The length of slice is 8
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The length of slice is 9
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The length of slice is 10
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Slice at 0 is 0
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Slice at 1 is 1
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Slice at 2 is 2
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Slice at 3 is 3
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Slice at 4 is 4
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Slice at 5 is 5
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Slice at 6 is 6
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Slice at 7 is 7
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Slice at 8 is 8
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Slice at 9 is 9
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另一个例子：
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```go
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var ar = [10]int{0,1,2,3,4,5,6,7,8,9}
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var a = ar[5:7] // reference to subarray {5,6} - len(a) is 2 and cap(a) is 5
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```
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将 a 重新分片：
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```go
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a = a[0:4] // ref of subarray {5,6,7,8} - len(a) is now 4 but cap(a) is still 5
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```
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**问题 7.7**
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1) 如果 a 是一个切片，那么 `s[n:n]` 的长度是多少？
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2) `s[n:n+1]` 的长度又是多少？
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## 链接
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- [目录](directory.md)
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- 上一节：[For-range 结构](07.3.md)
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- 下一节：[切片的复制与追加](07.5.md)
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