指向结构（或缺少结构）的指针

Question

假设我已经定义了这个结构：

type Vertex struct {
    X, Y float64
}

现在它是完全合法的去像这样使用它：

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

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

不过不用指针也可以:

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

两种情况下的结果是相同的，但它们在内部有何不同？使用指针会使程序运行更快吗？

PS。我知道 Abs() 函数需要一个指针作为接收者。这就解释了为什么稍后在 main 函数中使用指针的原因。但是为什么我不使用指针，直接在struct实例上调用Abs()，程序没有吐错呢？

Answer 1

why doesn't the program spit out an error when I don't use a pointer and directly call Abs() on a struct instance?

因为您可以获得指向结构实例（的地址）的指针。

如“What do the terms pointer receiver and value receiver mean in Golang?”中所述

Go will auto address and auto-dereference pointers (in most cases) so m := MyStruct{}; m.DoOtherStuff() still works since Go automatically does (&m).DoOtherStuff() for you.

如“Don't Get Bitten by Pointer vs Non-Pointer Method Receivers in Golang" or "Go 101: Methods on Pointers vs. Values", using a pointer receiver (v *Vertex) is great to avoid copy, since Go passes everything by value所示。

spec mentions (Method values):

As with method calls, a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value: t.Mp is equivalent to (&t).Mp.

指向结构（或缺少结构）的指针

Pointer to a struct (or lack thereof)

struct

pointers

go