go arrays and slices

What is an array?

Array

An array is a sequence of particular type elements composed of a fixed length, it may be composed of an array of zero or more elements

Array method definition?

method one

package main
import "fmt"

func arraytest()  {
    var x [3] int
    fmt.Println(x) 
}
// 输出 [0 0 0]
func main()  {
    arraytest()
    }

Use Quick declare an array

x3 :=[3] int {112,78}
fmt.Println(x3) 
输出 [112 78 0]

// get an array of values

var x2[3] int
    x2[0] = 1 //第一个元素
    x2[1] = 11
    x2[2] = 22 
    fmt.Println(x2) 
输出 [1 11 22]

// use a for loop to get the array of data

 x6 :=[...] int {3,5,6,82,34}
    for i :=0; i< len(x6);i++{
        fmt.Println(i,x6[i])
    }
    // 输出   如下 0 表示索引号， 3表示 对应的具体值
 0 3
 1 5
 2 6
 3 82
 4 34

Providing use range of language // go get in the way

for i,v := range x6{
fmt.Printf("%d of x6 is %d\n",i,v)
}
// 输出 
0 3
1 5
2 6
3 82
4 34

// only access elements

for _,v1 :=range x6 {
    fmt.Printf("x6 array value is %d\n",v1)
}
// 输出

0 of x6 is 3
1 of x6 is 5
2 of x6 is 6
3 of x6 is 82
4 of x6 is 34

slice

What is the slice (slice)?

Slice (Slice) is Golang the kind of special data structure, this data structure easier to use and manage data sets

// define slices

package main
import "fmt"

func slicetest() {
a1 :=[4] int {1,3,7,22}
fmt.Println(a1)

// 输出

[1 3 7 22]
var b1 []int = a1[1:4]
fmt.Println(b1,len(b1)) 

// 输出

[3 7 22] 3

}

func main() {
slicetest()
}

// make a statement using sections
make initialization function slice of time, if not indicate its capacity, he would be the same length and, if indicated its capacity during initialization

 s1 :=make([]int, 5) 
    fmt.Printf("The length of s1: %d\n",len(s1)) # 长度
    fmt.Printf("The capacity of; s1: %d\n",cap(s1)) # cap 容量
    fmt.Printf("The value of s1:%d\n",s1)
    // 输出 

    The length of s1: 5
The capacity of; s1: 5
The value of s1:[0 0 0 0 0]

    s12 :=make([]int, 5,8) # 指明长度为 5， 容量为8
    fmt.Printf("The length of s12: %d\n",len(s12))
    fmt.Printf("The capacity of; s12: %d\n",cap(s12))
    fmt.Printf("The value of s12:%d\n",s12)
    // 输出

    The length of s12: 5
The capacity of; s12: 8
The value of s12:[0 0 0 0 0]

// 
s3 := []int{1, 2, 3, 4, 5, 6, 7, 8}
s4 := s3[3:6]
fmt.Printf("The length of s4: %d\n", len(s4))
fmt.Printf("The capacity of s4: %d\n", cap(s4))
fmt.Printf("The value of s4: %d\n", s4)

// 输出

The length of s4: 3  # 长度为3 
The capacity of s4: 5 # 容量为5  
The value of s4: [4 5 6]  

// 切片与数组的关系

切片的容量可以看成是底层数组元素的个数
s4 是通过s3 切片获得来的，所以s3 的底层数组就是s4 的底层数组，切片是无法向左拓展的，所以s4 无法看到s3 最左边的三个元素，所以s4 的容量为5

// get sliced

before_slice :=[] int {1,4,5,23,13,313,63,23}
after_slice := before_slice[3:7]

fmt.Println("array before change",before_slice)

// 使用for range 遍历

for i := range after_slice{
    after_slice[i]++
}
fmt.Println("after cahnge",before_slice)

// output

array before change [1 4 5 23 13 313 63 23]
after cahnge [1 4 5 24 14 314 64 23]

The difference between arrays and slices

Whether capacity scalable? Array capacity can not stretch, slice can

It can be compared? // array of the same length may be compared