go array

go array characteristic

 

1、 Arrays are value types , Assigning and passing copies the entire array ,⽽ It's not a pointer .

func printArray(x [2]int) {
    
	fmt.Printf("the array x address is:%p\n", &x)
	x[1] = 1000
}

func test1()  {
    
	var a [2]int = [2]int {
    1}
	fmt.Printf("the array a address is:%p\n", &a)
	fmt.Printf("the value of a:%v\n", a)
	printArray(a)
}

Output ：

the array a address is:0xc0000a2070
the value of a:[1 0]
the array x address is:0xc0000a20a0

Value copy ⻉⾏ This will cause performance problems , It is usually suggested that ⽤ slice, Or array pointer .

 

2、 Array ⻓ Degree must be constant , And it's part of the type .[2]int and [3]int It's different types .

If the type is the same , Array ⽀ a “==”、"!=" The operator , Used to determine whether the values of the array are the same .

func test2() {
    
	a := [2]int {
    1,2}
	b := [2]int {
    1,2}

	// error:non-constant array bound length
	// var length int = 3
	// c := [length]int {}
	c := [3]int {
    }

	fmt.Printf("the type of a: %T, the value: %v\n", a, a)
	fmt.Printf("the type of b: %T, the value: %v\n", b, b)
	fmt.Printf("the type of c: %T, the value: %v\n", c, c)

	if a == b {
    
		fmt.Printf("a == b\n")
		fmt.Printf("the address of a: %p\n", &a)
		fmt.Printf("the address of b: %p\n", &b)
	}

	// error: invalid operation: a != c (mismatched types [2]int and [3]int)
	// if a != c {
    
	// fmt.Printf("a != c\n")
	// fmt.Printf("the address of a: %p\n", &a)
	// fmt.Printf("the address of c: %p\n", &c)
	// }

}

Output ：

he type of a: [2]int, the value: [1 2]
the type of b: [2]int, the value: [1 2]
the type of c: [3]int, the value: [0 0 0]
a == b
the address of a: 0xc000012090
the address of b: 0xc0000120a0

 

3、 Pointer array [n]*T, Array pointer *[n]T.

 

4、 Initialization of an array

func test3() {
    
	a := [3]int {
    1,2}				//  Uninitialized element value is  0.
	b := [...]int {
    1,2,3,4}			//  The array is determined by the initialization value ⻓ degree .
	c := [5]int {
    2:10, 4:100}		//  send ⽤ The index number initializes the element .
	d := [...]int {
    3:100, 5:100}	//  The index can be used to determine the length of the array 
    
	e := [...]struct {
    
		name string
		age int
	} {
    
		{
    "chen",25},				//  Element types can be omitted .
		{
    "yang",25},				//  Don't forget the last ⼀⾏ Comma of .
	}

	fmt.Printf("the type of a: %T, the value: %v\n", a, a)
	fmt.Printf("the type of b: %T, the value: %v\n", b, b)
	fmt.Printf("the type of c: %T, the value: %v\n", c, c)
	fmt.Printf("the type of d: %T, the value: %v\n", d, d)
	fmt.Printf("the type of e: %T, the value: %v\n", e, e)

}

Output ：

the type of a: [3]int, the value: [1 2 0]
the type of b: [4]int, the value: [1 2 3 4]
the type of c: [5]int, the value: [0 0 10 0 100]
the type of d: [6]int, the value: [0 0 0 100 0 100]
the type of e: [2]struct {
     name string; age int }, the value: [{
    chen 25} {
    yang 25}]

 

5、 Multidimensional arrays , First determine the number of columns , Then determine the number of rows .

func test4() {
    
	a := [2][3]int {
    {
    1,1,1}, {
    2,2,2}}
	b := [...][2]int {
    		//  The first  2  Latitude cannot ⽤ "...".
		{
    1,1},
		{
    2,2},
		{
    3,3},
	}

	fmt.Printf("the type of a: %T, the value: %v\n", a, a)
	fmt.Printf("the type of b: %T, the value: %v\n", b, b)
}

Output ：

the type of a: [2][3]int, the value: [[1 1 1] [2 2 2]]
the type of b: [3][2]int, the value: [[1 1] [2 2] [3 3]]

 

6、 The length of the array .

func test5() {
    
	a := [2]int {
    }
	fmt.Println("the len of a: ", len(a)," the cap of a: ", cap(a))
}

Output ：

the len of a:  2  the cap of a:  2

Built in functions len and cap Can return an array ⻓ degree ( Element quantity ).