Given a slice (not a pointer to a slice!) is there any way to truncate it in place?
The naive implementation doesn't work, because of scope:
package main
import (
"fmt"
)
func truncate(s []int, to int) []int{
s = s[:to] # <- has no effect outside this function
return s
}
func main() {
s := []int{0, 1, 2, 3, 4}
s1 := truncate(s, 3)
fmt.Printf("%v
", s1)
fmt.Printf("%v
", s)
}
prints
[0 1 2]
[0 1 2 3 4] # <- can we get [0 1 2] here?
Is there any way to modify the length or capacity of an existing slice, or are they immutable?
ETA: I thought this was obvious enough, but apparently not: when I ask whether it's possible to do this in place, I mean without reassigning s.
This is the way to go:
package main
import "fmt"
func main() {
s := []int{0, 1, 2, 3, 4}
s = truncate(s, 3)
fmt.Println(s) // [0 1 2]
}
func truncate(s []int, to int) []int {
return s[:to]
}
Slice is like a window to an underlying array.
The other way using pointer to the slice:
package main
import "fmt"
func main() {
s := []int{0, 1, 2, 3, 4}
truncate(&s, 3)
fmt.Println(s) // [0 1 2]
}
func truncate(s *[]int, to int) {
*s = (*s)[:to]
}