golang中切片copy复制和等号复制的区别介绍

func TestArr1(t *testing.T) {
 var a []int
 for i := 0; i < 100000000; i++ {
  a = append(a, i)
 }
 start := time.Now().UnixNano()
 var b = make([]int, 1000000)
 copy(b, a)
 end := time.Now().UnixNano()
 fmt.Println(end - start)
}

func TestArr2(t *testing.T) {
 var a []int
 for i := 0; i < 100000000; i++ {
  a = append(a, i)
 }
 start := time.Now().UnixNano()
 var b = a[0:1000000]
 end := time.Now().UnixNano()
 fmt.Println(end - start)
 _ = b
}

func TestArr1(t *testing.T) {
 var a []int
 for i := 0; i < 100; i++ {
  a = append(a, i)
 }
 var b = make([]int, 10)
 copy(b, a)
 a[0] = 999
 fmt.Println(b[0])
}

func TestArr2(t *testing.T) {
 var a []int
 for i := 0; i < 100; i++ {
  a = append(a, i)
 }
 var b = a[0:10]
 a[0] = 999
 fmt.Println(b[0])
}

var ar = [10]byte{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}
    var h, j []byte
    h = ar[2:5]
    j = ar[0:8]
    ar[2] = 'q'
    fmt.Println(string(h))
    fmt.Println(string(j))
    fmt.Printf("j容量%s\n", cap(j))
    fmt.Printf("j长度%s\n", len(j))
    x := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
    fmt.Println(x)
    fmt.Printf("x容量%s\n", cap(x))
    fmt.Printf("x长度%s\n", len(x))
    x = append(x, 11)
    fmt.Println(x)
    fmt.Printf("x容量%s\n", cap(x))
    fmt.Printf("x长度%s\n", len(x))
    var y []int
    for u := 0; u < 10; u++ {
        //y = append(y, fmt.Sprintf("%v", u))
        y = append(y, u)
    }
    fmt.Println(y)
    fmt.Printf("y容量%s\n", cap(y))
    fmt.Printf("y长度%s\n", len(y))
    y = append(y, 5)
    fmt.Println(y)
    var z = make([]int, len(y))
    copy(z, y)
    fmt.Println(z)
    y[0] = 9
    fmt.Println(y)
    fmt.Println(z)

for u := 0; u < 20; u++ {
        //y = append(y, fmt.Sprintf("%v", u))
        y = append(y, u)
        fmt.Printf("y长度%s\n", len(y))
        fmt.Printf("y容量%s\n", cap(y))
    }