Function for copying arrays in Go language

huangapple
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英文:

Function for copying arrays in Go language

问题

Go语言中是否有用于将一个数组复制到另一个数组的内置函数？在处理二维（或更高维）数组时，这个方法是否适用？

英文:

Is there any built-in function in Go for copying one array to another?
Will this work in case of two (or more) dimensional arrays?

答案1

得分: 39

Go语言中有一个内置函数可以将一个数组复制到另一个数组中，它就是copy函数。下面是一个示例：

  1. a := []string{
  2.     "hello",
  3.     "world",
  4. }
  5. b := []string{
  6.     "goodbye",
  7.     "world",
  8. }
  10. copy(a, b)
  12. // a == []string{"goodbye", "world"}

对于二维（或更高维）数组，copy函数只会进行浅拷贝。下面是一个示例：

  1. a := make([][]string, 10)
  3. b := make([][]string, 10)
  4. for i := range b {
  5.     b[i] = make([]string, 10)
  6.     for j := range b[i] {
  7.         b[i][j] = strconv.Itoa(i + j)
  8.     }
  9. }
  11. copy(a, b)
  13. // a和b看起来是一样的
  15. b[1] = []string{"some", "new", "data"}
  17. // b的第二行不同，但a仍然是一样的
  19. b[0][0] = "apple"
  21. // 现在a看起来不同了

如果你想要进行多维数组的深拷贝，目前没有内置的函数可以直接实现。你可以手动进行深拷贝，下面是一个示例：

  1. a := make([][]string, 10)
  3. b := make([][]string, 10)
  4. for i := range b {
  5.     b[i] = make([]string, 10)
  6.     for j := range b[i] {
  7.         b[i][j] = strconv.Itoa(i + j)
  8.     }
  9. }
  11. // 手动进行深拷贝
  12. for i := range b {
  13.     a[i] = make([]string, len(b[i]))
  14.     copy(a[i], b[i])
  15. }
  17. b[0][0] = "apple"
  19. // a仍然是一样的

需要注意的是，我假设你所说的"copy an array"是指"对切片进行深拷贝"，因为数组可以使用=运算符进行深拷贝。

英文:

> Is there any built-in function in Go language for copying one array to another?

Yes: http://play.golang.org/p/_lYNw9SXN5

  1. a := []string{
  2. 	"hello",
  3. 	"world",
  4. }
  5. b := []string{
  6. 	"goodbye",
  7. 	"world",
  8. }
  10. copy(a, b)
  12. // a == []string{"goodbye", "world"}

> Will this work in case of two (or more) dimensional arrays?

copy will do a shallow copy of the rows: http://play.golang.org/p/0gPk6P1VWh

  1. a := make([][]string, 10)
  3. b := make([][]string, 10)
  4. for i := range b {
  5. 	b[i] = make([]string, 10)
  6. 	for j := range b[i] {
  7. 		b[i][j] = strconv.Itoa(i + j)
  8. 	}
  9. }
  11. copy(a, b)
  13. // a and b look the same
  15. b[1] = []string{"some", "new", "data"}
  17. // b's second row is different; a still looks the same
  19. b[0][0] = "apple"
  21. // now a looks different

I don't think there's a built-in for doing deep-copys of multi-dimensional arrays: you can do it manually like: http://play.golang.org/p/nlVJq-ehzC

  1. a := make([][]string, 10)
  3. b := make([][]string, 10)
  4. for i := range b {
  5. 	b[i] = make([]string, 10)
  6. 	for j := range b[i] {
  7. 		b[i][j] = strconv.Itoa(i + j)
  8. 	}
  9. }
  11. // manual deep copy
  12. for i := range b {
  13. 	a[i] = make([]string, len(b[i]))
  14. 	copy(a[i], b[i])
  15. }
  17. b[0][0] = "apple"
  19. // a still looks the same

edit: As pointed out in the comments, I assumed by "copy an array" you meant "do a deep copy of a slice", as arrays can be deep-copied with the = operator as per jnml's answer (because arrays are value types): http://play.golang.org/p/8EuFqXnqPB

答案2

得分: 22

在Go语言中，复制数组的主要方法是使用赋值运算符=，这对于任何其他类型的值也是如此。

  1. package main
  3. import "fmt"
  5. func main() {
  6.     var a, b [4]int
  7.     a[2] = 42
  8.     b = a
  9.     fmt.Println(a, b)
  11.     // 2D array
  12.     var c, d [3][5]int
  13.     c[1][2] = 314
  14.     d = c
  15.     fmt.Println(c)
  16.     fmt.Println(d)
  17. }

输出结果：

  1. [0 0 42 0] [0 0 42 0]
  2. [[0 0 0 0 0] [0 0 314 0 0] [0 0 0 0 0]]
  3. [[0 0 0 0 0] [0 0 314 0 0] [0 0 0 0 0]]

Playground

英文:

The primary "function" for copying an array in Go is the assignment operator =, as it is the case for any other value of any other type.

  1. package main
  3. import "fmt"
  5. func main() {
  6.         var a, b [4]int
  7.         a[2] = 42
  8.         b = a
  9.         fmt.Println(a, b)
  11.         // 2D array
  12.         var c, d [3][5]int
  13.         c[1][2] = 314
  14.         d = c
  15.         fmt.Println(c)
  16.         fmt.Println(d)
  17. }

Playground

Output:

  1. [0 0 42 0] [0 0 42 0]
  2. [[0 0 0 0 0] [0 0 314 0 0] [0 0 0 0 0]]
  3. [[0 0 0 0 0] [0 0 314 0 0] [0 0 0 0 0]]

答案3

得分: 10

使用copy函数将切片a的元素复制到数组b中。

  1. a := []int{1, 2, 3}
  2. var b [3]int
  4. fmt.Println("A:", a)
  5. fmt.Println("B:", b)
  7. copy(b[:], a)
  9. fmt.Println("A:", a)
  10. fmt.Println("B2:", b)
  12. b[1] = 9
  14. fmt.Println("A:", a)
  15. fmt.Println("B3:", b)

输出结果：

  1. A: [1 2 3]
  2. B: [0 0 0]
  3. A: [1 2 3]
  4. B2: [1 2 3]
  5. A: [1 2 3]
  6. B3: [1 9 3]
英文:

Use copy http://play.golang.org/p/t7P6IliMOK

  1. a := []int{1, 2, 3}
  2. var b [3]int
  4. fmt.Println("A:", a)
  5. fmt.Println("B:", b)
  7. copy(b[:], a)
  9. fmt.Println("A:", a)
  10. fmt.Println("B2:", b)
  12. b[1] = 9
  14. fmt.Println("A:", a)
  15. fmt.Println("B3:", b)

OUT:

  1. A: [1 2 3]
  2. B: [0 0 0]
  3. A: [1 2 3]
  4. B2: [1 2 3]
  5. A: [1 2 3]
  6. B3: [1 9 3]

huangapple
  • 本文由 发表于 2013年9月1日 23:19:32
  • 转载请务必保留本文链接：https://go.coder-hub.com/18559830.html
  • arrays
  • go
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