JuniorTheoryVery common

What does the program print?

package main

import "fmt"

func change(n int, p *int, s []int) {
    n, *p, s[0] = 10, 20, 30
}
func main() {
    a, b, s := 1, 2, []int{3}
    change(a, &b, s)
    fmt.Println(a, b, s[0])
}

1 20 30

Expecting 10 20 30: Go passes every argument by value, so n is a copy of a, and writing to it leaves a at 1.
Expecting 1 20 3: the slice header is copied, but the copy points to the same array, so s[0] = 30 is seen in main.

Why does appending to a slice inside a function sometimes not show up outside?
How does a pointer receiver method differ from a value receiver here?

Back to questions Open topic in roadmap →Answer it yourself — Quiz

Back to questions

JuniorTheoryVery common

What does the program print?

package main

import "fmt"

func change(n int, p *int, s []int) {
    n, *p, s[0] = 10, 20, 30
}
func main() {
    a, b, s := 1, 2, []int{3}
    change(a, &b, s)
    fmt.Println(a, b, s[0])
}

1 20 30

Expecting 10 20 30: Go passes every argument by value, so n is a copy of a, and writing to it leaves a at 1.
Expecting 1 20 3: the slice header is copied, but the copy points to the same array, so s[0] = 30 is seen in main.

Why does appending to a slice inside a function sometimes not show up outside?
How does a pointer receiver method differ from a value receiver here?

Back to questions Open topic in roadmap →Answer it yourself — Quiz