Go slice

The length of a Go array cannot be changed, making it less suitable for certain scenarios. Therefore, Go provides a flexible and powerful built-in type: Slice (similar to a dynamic array), which allows appending elements, potentially increasing the slice's capacity during appending.

var variableName []DataType

1. A slice is a reference to an array, making it a reference type. However, a slice itself is a struct, and its value is passed by copy.
2. The length of a slice can change, so a slice can be seen as a dynamic array.
3. The traversal method for a slice is the same as that for an array.
4. If slice == nil, then both len(slice) and cap(slice) will result in 0.

Regular Definition：

    var s1 []type
or
    s1 := []type{}

Using make：

    var s2 []type = make([]type, length, capacity) //length is the length of the array and also the initial length of the slice
or
    s2 := make([]type, length, capacity) //capacity is an optional parameter used to specify the capacity

s := []int{9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
s2 := s[:]
s3 := s[1:]
s4 := s[:8]
s5 := s[1:8]
fmt.Println(s2, s3, s4, s5)

#[9 8 7 6 5 4 3 2 1 0] [8 7 6 5 4 3 2 1 0] [9 8 7 6 5 4 3 2] [8 7 6 5 4 3 2]

append adds elements to the end of a slice and returns the new slice object.

#func append(slice []Type, elems ...Type) []Type

s := []int{9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
s2 := append(s, -1)
fmt.Println(s2)

#[9 8 7 6 5 4 3 2 1 0 -1]

When the slice's capacity is exceeded (exceeded slice.cap), a new slice (with a new memory address) is created, the content of the old slice is copied to the new slice, new_slice_cap = 2*old_slice_cap + N  (where N is an integer multiple of 2), until the new slice can accommodate all elements.

s := []int{9, 8, 7, 6}
s3 := s[:3]
fmt.Println("old slice:", s3, "old 1st item address:", &s3[0], "len", len(s3), "cap:", cap(s3))

s3 = append(s3, 10, 11, 12, 13, 14, 15, 16)
fmt.Println("new slice:", s3, "new 1st item address:", &s3[0], "len", len(s3), "cap:", cap(s3))

#old slice: [9 8 7] old 1st item address: 0xc0003dc960 len 3 cap: 4
#new slice: [9 8 7 10 11 12 13 14 15 16] new 1st item address: 0xc00002b2c0 len 10 cap: 10

Copies elements from a source slice to a destination slice. If the destination slice is shorter than the source slice, only as many elements as fit into the destination slice are copied. Elements at corresponding positions in the destination slice are overwritten.

#func copy(dst []Type, src []Type) int

s1 := []int{1, 2, 3, 4, 5}
fmt.Println("slice s1:", s1)

s2 := make([]int, 10)
fmt.Println("slice s2:", s2)

s3 := []int{10, 9, 8, 7}
fmt.Println("slice s3:", s3)

copy(s2, s1)
copy(s3, s1)
fmt.Println("copied slice s1:", s1)
fmt.Println("copied slice s2:", s2)
fmt.Println("copied slice s3:", s3)

#slice s1: [1 2 3 4 5]
#slice s2: [0 0 0 0 0 0 0 0 0 0]
#slice s3: [10 9 8 7]
#copied slice s1: [1 2 3 4 5]
#copied slice s2: [1 2 3 4 5 0 0 0 0 0]
#copied slice s3: [1 2 3 4]

for key, val := range s1 {
    //...  
}

At its core, a string is just a byte array, therefore, it can also be sliced.

str1 := "hello world"
s1 := str1[0:5]
fmt.Println(s1)

str2 := "你好，世界！"
s := []rune(str2)
s[3] = '闪'
s[4] = '光'
s[5] = '创'
s = append(s, '世')
fmt.Println(string(s))

#hello
#你好，闪光创世

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