Golang Arrays and slices

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Get a better understanding of golang arrays and slices with the following questions

2. Type

   An array is a value type, and when you assign an array to another array, you pass a copy.
   A slice is a reference type, and an array of tile wrappers is called the underlying array of the slice.
   Let's take a look at the code

   //a是一个数组，注意数组是一个固定长度的，初始化时候必须要指定长度，不指定长度的话就是切片了a := [3]int{1, 2, 3}//b是数组，是a的一份拷贝b := a//c是切片，是引用类型，底层数组是ac := a[:]for i := 0; i < len(a); i++ {  a[i] = a[i] + 1}//改变a的值后，b是a的拷贝，b不变，c是引用，c的值改变fmt.Println(a) //[2,3,4]fmt.Println(b) //[1 2 3]fmt.Println(c) //[2,3,4]

4. Make
   Make can only be used for slice, map and channel, so the following section of code generates a slice, which is a reference type

   s1 := make([]int, 0, 3)for i := 0; i < cap(s1); i++ {    s1 = append(s1, i)}s2 := s1for i := 0; i < len(a); i++ {    s1[i] = s1[i] + 1}fmt.Println(s1)  //[1 2 3]fmt.Println(s2)  //[1 2 3]

6. When the slice append exceeds the bounds of the underlying array

   //n1是n2的底层数组n1 := [3]int{1, 2, 3}n2 := n1[0:3]fmt.Println("address of items in n1: ")for i := 0; i < len(n1); i++ {    fmt.Printf("%p\n", &n1[i])}//address of items in n1://0xc20801e160//0xc20801e168//0xc20801e170fmt.Println("address of items in n2: ")for i := 0; i < len(n2); i++ {    fmt.Printf("%p\n", &n2[i])}//address of items in n2://0xc20801e160//0xc20801e168//0xc20801e170//对n2执行append操作后，n2超出了底层数组n1的jn2 = append(n2, 1)fmt.Println("address of items in n1: ")for i := 0; i < len(n1); i++ {    fmt.Printf("%p\n", &n1[i])}//address of items in n1://0xc20801e160//0xc20801e168//0xc20801e170fmt.Println("address of items in n2: ")for i := 0; i < len(n2); i++ {    fmt.Printf("%p\n", &n2[i])}//address of items in n2://0xc20803a2d0//0xc20803a2d8//0xc20803a2e0//0xc20803a2e8

7. Reference "Invalid"
   Implements a function to delete slice last item

   func rmLast(a []int) {    fmt.Printf("[rmlast] the address of a is %p", a)    a = a[:len(a)-1]    fmt.Printf("[rmlast] after remove, the address of a is %p", a)}

   After calling this function, it is found that the original slice has not changed

   func main() {    xyz := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}    fmt.Printf("[main] the address of xyz is %p\n", xyz)    rmLast(xyz)    fmt.Printf("[main] after remove, the address of xyz is %p\n", xyz)    fmt.Printf("%v", xyz) //[1 2 3 4 5 6 7 8 9]}

   The results are printed as follows:

   [main] the address of xyz is 0xc2080365f0[rmlast] the address of a is 0xc2080365f0[rmlast] after remove, the address of a is 0xc2080365f0[main] after remove, the address of xyz is 0xc2080365f0[1 2 3 4 5 6 7 8 9]

   Here the slice pointer value is printed directly, because slice is a reference type, so the pointer values are the same, we replace the print slice address to see

   func rmLast(a []int) {    fmt.Printf("[rmlast] the address of a is %p", &a)    a = a[:len(a)-1]    fmt.Printf("[rmlast] after remove, the address of a is %p", &a)}func main() {    xyz := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}    fmt.Printf("[main] the address of xyz is %p\n", &xyz)    rmLast(xyz)    fmt.Printf("[main] after remove, the address of xyz is %p\n", &xyz)    fmt.Printf("%v", xyz) //[1 2 3 4 5 6 7 8 9]}

   Results:

   [main] the address of xyz is 0xc20801e1e0[rmlast] the address of a is 0xc20801e200[rmlast] after remove, the address of a is 0xc20801e200[main] after remove, the address of xyz is 0xc20801e1e0[1 2 3 4 5 6 7 8 9]

   This time you can see that slice is actually copying a copy of the slice as a function parameter, because slice itself is a pointer, so from a phenomenon, slice is a reference type.