Go language -- detailed explanation of slice

Blog description

Explain

Go language slicing is an abstraction of arrays.

The length of go array cannot be changed, and such a set is not suitable in a specific scene. Go provides a flexible and powerful built-in type slice ("dynamic array"), which is not fixed compared with array, and can append elements. When appending, it may increase the capacity of slice.

Defining slices

Note: the length of the slice does not need to be specified

1. Declare an array of unspecified size to define slices

var identifier []type
//for example
var slice []int

2. Use the make() function to create slices

var slice1 []type = make([]type, len)
//It can also be abbreviated as
slice1 := make([]type, len)
//for example
slice := make([]type, len)

Slices are indexable

len() and cap() functions

The length can be obtained by the len() method.

Slicing provides a way to calculate capacity cap() can measure the maximum length of slicing

package main

import "fmt"

func main(){
	var number = make([]int,3,5)
	fmt.Printf("len=%d cap=%d 		slice=%v\n",len(number),cap(number),number)
}

//len=3 cap=5 slice=[0 0 0]

Nil slice

A slice is nil by default and 0 in length before it is initialized

package main

import "fmt"

func main(){
	var number []int
	fmt.Printf("len=%d cap=%d slice=%v\n",len(number),cap(number),number)
}

//len=0 cap=0 slice=[]

Slicing

You can set the lower bound and upper bound to cut slices [lower bound: upper bound]

package main

import "fmt"

func main() {
	//Create slice
	number := []int{0, 1, 2, 3, 4, 5, 6, 7, 8}
	printSlice(number)

	//Print original slice
	fmt.Println("number == ", number)

	//Print sub slice from index 1 to index 4
	fmt.Println("number == ", number[1:4])

	//Print sub slice default lower limit
	fmt.Println("number == ", number[:3])

	//Default upper limit of print subsegment
	fmt.Println("number == ", number[4:])

}

func printSlice(x []int) {
	fmt.Printf("len=%d cap=%d slice=%v\n", len(x), cap(x), x)
}

Result

Increase slice capacity

Principle: create a new and larger slice and copy the contents of the original slice

append() and copy() functions

package main

import (
	"fmt"
)

func main() {
	//Create slice
	var number []int
	printSlice(number)

	//Allow appending empty slices
	number = append(number,0)
	printSlice(number)

	//Add an element to the slice
	number = append(number,1)
	printSlice(number)

	//Add multiple elements at the same time
	number = append(number,2,3,4)
	printSlice(number)

	//New slices created are twice the capacity of previous slices
	number1 := make([]int,len(number),(cap(number))*2)

	//Copy number to number1
	copy(number1,number)
	printSlice(number1)
}

func printSlice(x []int) {
	fmt.Printf("len=%d cap=%d slice=%v\n", len(x), cap(x), x)
}

Thank