Golang Program to Add Elements to a Slice

In this tutorial, we will learn how to add elements to a slice using different examples. A slice is a sequence of elements just like an array. An array is a fixed sequence of elements whereas slice is a dynamic array which means its value is not fixed and can be changed. Slices are more efficient and faster than arrays moreover they are passed by reference instead by value. Let's go through the example to understand things.

Method 1: Using append function with strings

In this method, we will use append function to add string elements to the slice. We have used an append function which is a built-in function whose features are described below. Let's have a look and see how its executed.

Syntax

func append(slice, element_1, element_2?, element_N) []T

The append function is used to add values to an array slice. It takes number of arguments. The first argument is the array to which we wish to add the values followed by the values to add. The function then returns the final slice of array containing all the values.

Algorithm

• Step 1 ? Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and output.

• Step 2 ? Create a function main and in that function create a slice with name countries and print it on console.

• Step 3 ? Now use append function to add new string elements to the slice and assign this to a variable named new_countries.

• Step 4 ? Print the value stored in new_countries on console using fmt.Println() function where ln refers to new line.

Example

Golang program to add elements in a slice using append function with strings

package main
import "fmt"
func main() {
           
   // create a slice of type string
   Countries := []string{"Iceland", "Switzerland"}
   fmt.Println("The slice before adding of elements is:", Countries)
           
   // append new elements and old slice in new slice
   new_countries := append(Countries, "Canada", "Italy")
   fmt.Println("The new slice after adding elements is:")
   fmt.Println(new_countries) // print new slice
}

Output

The slice before adding of elements is: [Iceland Switzerland]
The new slice after adding elements is:
[Iceland Switzerland Canada Italy]

Method 2: Using copy function

Syntax

In this method, we will use copy function to add elements to the slice. The copy function is a built-in function whose features are described below. Let's inculcate the steps required to execute the program.

func copy(dst, str[] type) int 

The copy function in go language is used to copy the values of one source array to the destination array and returns the number of elements copied as the result. It takes the two arrays as an argument.

Algorithm

• Step 1 ? Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and output.

• Step 2 ? Create a function main and in that function create a slice with name countries and print it on console.

• Step 3 ? Create another slice of type string and copy its contents to the old slice.

• Step 4 ? Print the contents of old slice after elements are copied on the screen using fmt.Println() function.

Example

Golang program to add elements in a slice using copy function

package main
import "fmt"
func main() {
         
   // create a slice of type string
   countries := []string{"Canada", "Italy"}
   fmt.Println("The slice before adding element is:", countries)
   morecountries := []string{"Finland", "Switzerland"}

   // create a new slice to copy the elements of slice
   new_slice := copy(countries, morecountries)
   fmt.Println("The slice after adding element in slice is:")
   fmt.Println("The new slice we created has", new_slice, "elements->", countries)
}

Output

The slice before adding element is: [Canada Italy]
The slice after adding element in slice is:
The new slice we created has 2 elements-> [Finland Switzerland]

Method 3: Using append function with integer values

In this method, we will use append function to add integer elements to the slice. We have used an append function which is a built-in function whose features are described below. Let's have a look and see how its executed.

Syntax

func append(slice, element_1, element_2?, element_N) []T

The append function is used to add values to an array slice. It takes number of arguments. The first argument is the array to which we wish to add the values followed by the values to add. The function then returns the final slice of array containing all the values.

Algorithm

• Step 1 ? Create a package main and declare fmt(format package) package in the program where main produces executable codes and fmt helps in formatting input and output.

• Step 2 ? Create a function main and in that function create a slice with name numbers and print it on console.

• Step 3 ? Now use append function to add new integer elements to the slice and assign this to a variable named new_numbers.

• Step 4 ? Print the value stored in new_numbers on console using fmt.Println() function where ln refers to new line.

Example

package main
import "fmt"
func main() {

   // create a slice of type int
   numbers := []int{1, 2}
   fmt.Println("The slice before adding of elements is:", numbers)

   // append new elements in the slice
   new_numbers := append(numbers, 3, 4) 
   fmt.Println("The new slice after adding elements is:")

   // print new slice
   fmt.Println(new_numbers)  
}

Output

The slice before adding of elements is: [1 2]
The new slice after adding elements is:
[1 2 3 4]

Conclusion

We executed the program of adding the elements to a slice using three examples. In the first example we have used an append function to add the string elements, in the second example we have used the copy function to add values and in the third example we have used an append function to add the integer elements.Both the examples give similar output. Hence the program executed successfully.