// +build OMIT 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)) }