Go Slice Functions - append and copy - Code Example

If you are new to Slices read the basics of slices here.

Go has two built-in functions to facilitate appending and copying with Slices:

1. append

As explained in the last article, unlike the fixed length arrays slices are dynamic in nature. append is a function that facilitate expansion of slices.

2. copy

copy function copies elements from a source to destination & returns the number of elements copied.

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package main import "fmt" func main() { slice1 := []int{11,22,33,44,55} fmt.Println("Slice1 = ", slice1) slice2 := append(slice1, 66,77,88) fmt.Println("Slice2 = ", slice2) slice3 := append(slice1, 99) fmt.Println("Slice3 = ", slice3) slice4 := append(slice2, 99) fmt.Println("Slice4 = ", slice4) sliceWorkingDays := []string{"Mon", "Tue", "Wed", "Thu", "Fri"} sliceWeekDays := append(sliceWorkingDays, "Sat", "Sun") fmt.Println("Working Days = ", sliceWorkingDays ) fmt.Println("Week Days = ", sliceWeekDays) fmt.Println("Weekends =", sliceWeekDays[5:]) }

Output

You can play with the above code.

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package main import "fmt" func main() { slice1 := []int{1,2,3} slice2 := make([]int, 3) // Change 3 to 1 and note the results slice3 := []int{2,4,6} copy(slice2, slice1) fmt.Println("Slice1 = ", slice1, "| Slice2 = ", slice2) copy(slice2, slice3) fmt.Println("Slice1 = ", slice1, "| Slice2 = ", slice2, "| Slice3 = ", slice3) }

You can play with the above code here

Question

What is the output of below snippet?

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package main import "fmt" func main() { slice1 := []int{1,3,5,7} slice2 := []int{2,4,6,8} fmt.Println("Slice1 = ", slice1, "| Slice2 = ", slice2) copy(slice2, slice1[:]) fmt.Println("Slice1 = ", slice1, "| Slice2 = ", slice2) }

Answer