JuniorTheoryCommon

What does the program print?

package main

import "fmt"

type Point struct{ X, Y int }

func main() {
    p := Point{X: 1, Y: 2}
    q, r := p, &p
    r.X = 9
    fmt.Println(q.X, p.X)
}

1 9

Expecting q to change too: q := p copies every field of the struct, so q is a separate Point that keeps X equal to 1.
Expecting r.X = 9 to need (*r).X: Go dereferences a pointer to a struct for you, so r.X writes the field of p itself.

What would fmt.Println(r.X) print at the end of the program?
How would you pass a Point to a function so that the function can change it?

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JuniorTheoryCommon

What does the program print?

package main

import "fmt"

type Point struct{ X, Y int }

func main() {
    p := Point{X: 1, Y: 2}
    q, r := p, &p
    r.X = 9
    fmt.Println(q.X, p.X)
}

1 9

Expecting q to change too: q := p copies every field of the struct, so q is a separate Point that keeps X equal to 1.
Expecting r.X = 9 to need (*r).X: Go dereferences a pointer to a struct for you, so r.X writes the field of p itself.

What would fmt.Println(r.X) print at the end of the program?
How would you pass a Point to a function so that the function can change it?

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