Sub-slice

Learn the slice slicing syntax.

Sub-slices

The expression s[start:end] gives a sub-slice from index start up to, but not including, index end. Either bound can be omitted:

s := []string{"a", "b", "c", "d", "e"}
fmt.Println(s[1:3])  // [b c]
fmt.Println(s[:2])   // [a b]
fmt.Println(s[3:])   // [d e]

A sub-slice doesn't create a new array; it shares the same one. Changing the sub-slice changes the original too.

Appending to a sub-slice overwrites the original slice's next elements if there is capacity:

s := []int{1, 2, 3, 4}
ilk := s[:2]           // [1 2], cap 4
ilk = append(ilk, 99)
fmt.Println(s)         // [1 2 99 4]  ← 3 was overwritten!

To prevent this, three-index slicing limits the capacity: s[:2:2]. Then append allocates a new array.

Declare s := []int{1, 2, 3, 4, 5}. Take orta := s[1:4], set orta[0] = 20 and print both orta and s on one line (see the sharing).

Show example solution

package main

import "fmt"

func main() {
    s := []int{1, 2, 3, 4, 5}
    orta := s[1:4]
    orta[0] = 20
    fmt.Println(orta, s)
}

Last two elements

s := []string{"a", "b", "c", "d"}
son := s[____]  // [c d]

Show answer

s := []string{"a", "b", "c", "d"}
son := s[2:]  // [c d]

Next lesson: len and cap