Go Learning notes: arrays

This is a creation in Article, where the information may have evolved or changed.

• An array is a group of elements that have an 相同数据类型 element 固定长度 有序集合 .
  

• In the go language, arrays are value types, and lengths are part of a type, meaning " [10]int and" [20]int are two completely different types of arrays.
  

• Two arrays of the same type support a comparison of "= =" and "! =", but cannot compare size.
  

• Array as a parameter, the inside of the function does not change the value inside the array unless it is a pointer to the incoming array.
  

• Pointers to arrays: *[3]int
  

• Array of pointers: [2]*int

Example 1:

package mainimport  "FMT" Func main ()  {    //  Here we have created an array of integers with 5 elements The data type and array length of the     //  element are part of the arrays     //  by default, array elements are 0 values      //  for integers, the value of 0 is 0    var a [5]int    fmt. Println ("EMP:",  a)     //  We can use an index to set the value of an array element, like this     //  " Array[index] = value "   or use an index to get the element value,    //  like this" Array[index "     a[4] = 100    fmt. Println ("Set:",  a)     fmt. Println ("Get:",  a[4])     //  The built-in Len function returns the length of the array     fmt. Println ("Len:",  len (a))     //  This method can define and initialize an array     b&nbsp at the same time;: = [5]int{1, 2, 3, 4, 5}    fmt. Println ("DCL:",  b) &NBSP;&NBSP;&NBSP;&NBSP;//&NThe array is one-dimensional, but you can define the elements of the array as an array     //  to get the multidimensional array structure &NBSP;&NBSP;&NBSP;&NBSP;VAR&NBSP;TWOD  [2][3]int    for i := 0; i < 2; i++ {         for j := 0; j < 3; j++  {            twod[i][j] = i +  j        }    }    fmt. Println ("2d: ",  twod)}

The output result is

EMP: [0 0 0 0 0]set: [0 0 0 0 100]GET:100LEN:5DCL: [1 2 3 4 5]2d: [[0] 1 2] [1 2 3]]

拥有固定长度is a feature of the array, but this feature can sometimes cause a lot of inconvenience, especially if the number of elements in a set is not fixed. This time we use more 切片 .

Example 2:

You can create an array with new and return a pointer to the array

Package Mainimport "FMT" Func Main () {var a = new ([5]int) test (a) fmt. Println (A, Len (a))}func test (a *[5]int) {a[1] = 5}

Output results

&[0 5 0 0 0] 5

Example 3:

Package Mainimport "FMT" Func Main () {a: = [...] user{{0, "User0"}, {8, "User8"},} B: = [...] *user{{0, "User0"}, {8, "User8"},} FMT. Println (A, Len (a)) fmt. Println (b, Len (b))}type User struct {Id int Name string}

Output results

[{0 User0} {8 User8}] 2[0x1f216130 0x1f216140] 2

Example 4 (exercise):

package main import  (         "FMT")  func main ()  {         var arr_1 [10]int         var sum int         fmt. Println ("\nlen (arr_1): ",  len (arr_1))         fmt. Println ("initial value of arr_1:")         for _,  elem := range arr_1 {                 fmt. Print (elem,  " ")         }         fmt. Println ("\ninitial value of sum: ", sum,  "\ n")           fmt. Println ("arr_1:")          for i := 0; i < len (arr_1); i++ {                 arr_1[i] = len (arr_1)  -  1 - i                 fmt. Println (Arr_1[i])         }          fmt. Println ("\neach set of range arr_1:\nidx val\n-------")          for idx, val := range arr_1 {                 fmt. Println (Idx, val)         }          for _, elem := range arr_1 {                 sum += elem        }          fmt. Print ("\nsum of arr_1: ", sum,  "\ n")           // define array with length unknown, must initialize when  defining        var arr_2 = [...] string{                 "Sun",                  "Air",                  "Water"}         fmt. Println ("arr_2:")         for _, elem := range  arr_2 {       &nbsP;        fmt. Println (Elem)         }          fmt. Println ()}

Output results

Len (arr_1): 10initial value of arr_1:0 0 0 0 0 0 0 0 0 0 Initial value of sum:0 Arr_1:9876543210each set of range arr_1 : idx val-------0 approx. 0sum of Arr_1:45arr_2:sunairwater