Go Slice Prepend

In Go, prepending to a slice involves adding an element or elements to the beginning of the slice. While Go does not have a built-in method for prepending, you can achieve it by creating a new slice and using the append() function.

In this tutorial, we will explore how to prepend elements to a slice in Go, demonstrate practical examples, and provide detailed explanations.

Steps to Prepend to a Slice

  • Create a New Slice: Define a new slice that will hold the prepended elements.
  • Use append(): Append the original slice to the new slice containing the prepended elements.
  • Reassign the Slice: Assign the result back to the original slice variable if needed.

Examples of Prepending to a Slice

1. Prepend a Single Element

This example demonstrates how to prepend a single element to a slice:

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package main

import "fmt"

func main() {
    // Original slice
    slice := []int{20, 30, 40}

    // Prepend an element
    slice = append([]int{10}, slice...)

    // Print the result
    fmt.Println("Prepended Slice:", slice)
}

Explanation

  1. Create Original Slice: The slice slice is initialized with integers {20, 30, 40}.
  2. Create New Slice: A new slice containing the element 10 is created inline using []int{10}.
  3. Use append(): The append() function combines the new slice with the original slice, prepending the element.
  4. Reassign the Slice: The result is reassigned to slice.

Output

2. Prepend Multiple Elements

This example demonstrates how to prepend multiple elements to a slice:

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package main

import "fmt"

func main() {
    // Original slice
    slice := []int{30, 40, 50}

    // Prepend multiple elements
    slice = append([]int{10, 20}, slice...)

    // Print the result
    fmt.Println("Prepended Slice:", slice)
}

Explanation

  1. Create Original Slice: The slice slice is initialized with integers {30, 40, 50}.
  2. Create New Slice: A new slice containing the elements {10, 20} is created inline using []int{10, 20}.
  3. Use append(): The append() function combines the new slice with the original slice, prepending the elements.
  4. Reassign the Slice: The result is reassigned to slice.

Output

Points to Remember

  • Efficient Prepending: Prepending in Go involves creating a new slice and combining it with the original slice.
  • Use append(): The append() function with the ... operator simplifies the prepending process.
  • Memory Considerations: Prepending creates a new slice, so memory allocation is involved.
  • Flexible Operation: The same technique works for slices of any type, such as integers, strings, or structs.