> it seems that it should be expected that an a.Change func will mutate A But you can make functions that have copied receivers: type Foo struct {

> it seems that it should be expected that an a.Change func will mutate A But you can make functions that have copied receivers: type Foo struct { bar int } func (f Foo) mutate() { f.bar = 2 } func main() { f := Foo{bar: 1} f.mutate() fmt.Println(f.bar) // 1 } > whats the advantage of creating a function of type struct a rather than creating the C equivalent of change(obj structAtype) types need to have methods in order to fulfill interfaces, that's all. (Well, and all the downstream benefits of using interfaces, such a polymorphism).