JuniorTheoryCommon

What does the program print?

package main

import "fmt"

func main() {
    a := [3]int{1, 2, 3}
    b := a
    b[0] = 9
    fmt.Println(a[0], b[0])
}

1 9

Expecting 9 9, as if b shared the array with a: assigning an array copies all its elements, so writing to b[0] leaves a unchanged.
Expecting a compile error, as in C, where arrays cannot be assigned: in Go b := a is legal and copies the whole array.

How would you make b see the same elements as a?
What happens to the caller's array when a function receives it as a [3]int parameter and changes it?

JuniorTheoryCommon

package main

import "fmt"

func main() {
    a := [3]int{1, 2, 3}
    b := a
    b[0] = 9
    fmt.Println(a[0], b[0])
}

1 9

Expecting 9 9, as if b shared the array with a: assigning an array copies all its elements, so writing to b[0] leaves a unchanged.
Expecting a compile error, as in C, where arrays cannot be assigned: in Go b := a is legal and copies the whole array.

How would you make b see the same elements as a?
What happens to the caller's array when a function receives it as a [3]int parameter and changes it?