I' trying to move an item from one position to another inside a slice. Go Playground
indexToRemove := 1
indexWhereToInsert := 4
slice := []int{0,1,2,3,4,5,6,7,8,9}
slice = append(slice[:indexToRemove], slice[indexToRemove+1:]...)
fmt.Println("slice:", slice)
newSlice := append(slice[:indexWhereToInsert], 1)
fmt.Println("newSlice:", newSlice)
slice = append(newSlice, slice[indexWhereToInsert:]...)
fmt.Println("slice:", slice)
This produces to following output:
slice: [0 2 3 4 5 6 7 8 9]
newSlice: [0 2 3 4 1]
slice: [0 2 3 4 1 1 6 7 8 9]
But I would expect the output be like this:
slice: [0 2 3 4 5 6 7 8 9]
newSlice: [0 2 3 4 1]
slice: [0 2 3 4 1 **5** 6 7 8 9]
Where is my fault?
The problem is that newSlice is not a distinct copy of slice--they reference the same underlying array.
So when you assign to newSlice, you're modifying the underlying array, and thus slice, too.
To remedy this, you need to make an explicit copy:
package main
import (
"fmt"
)
func main() {
indexToRemove := 1
indexWhereToInsert := 4
slice := []int{0,1,2,3,4,5,6,7,8,9}
val := slice[indexToRemove]
slice = append(slice[:indexToRemove], slice[indexToRemove+1:]...)
fmt.Println("slice:", slice)
newSlice := make([]int, indexWhereToInsert+1)
copy(newSlice,slice[:indexWhereToInsert])
newSlice[indexWhereToInsert]=val
fmt.Println("newSlice:", newSlice)
fmt.Println("slice:", slice)
slice = append(newSlice, slice[indexWhereToInsert:]...)
fmt.Println("slice:", slice)
}
(Note that I've also added the val variable, rather than hardcoding 1 as the value to be inserted.)