Tour of Go 2.0

Pointers and functions

Same logic, different form. Here Abs and Scale are plain functions, not methods.

Notice that Scale takes a *Vertex — it must, because it needs to mutate the value. And the call site has to pass &v explicitly.

Try it: remove the * from Scale’s parameter on line 16. What breaks? What else do you have to change to make it compile again?

main.go ▶ Run in Playground 
package main

import (
	"fmt"
	"math"
)

type Vertex struct {
	X, Y float64
}

func Abs(v Vertex) float64 {
	return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

func Scale(v *Vertex, f float64) {
	v.X = v.X * f
	v.Y = v.Y * f
}

func main() {
	v := Vertex{3, 4}
	Scale(&v, 10)
	fmt.Println(Abs(v))
}