向量分配是通过值还是通过引用以Google的Go语言复制的？

Question

In the following code, I create one peg puzzle then do a move on it which adds a move to its movesAlreadyDone vector. Then I create another peg puzzle then do a move on it which adds a move to its movesAlreadyDone vector. When I print out the values in that vector for the second one, it has the move in it from the first one along with the move from the second one. Can anyone tell me why it seems to be assigning by reference and not value? Are vector assignments copied by value or by reference in Google's Go language?

package main

import "fmt"
import "container/vector"

type Move struct { x0, y0, x1, y1 int }

type PegPuzzle struct {
    movesAlreadyDone * vector.Vector;
}

func (p *PegPuzzle) InitPegPuzzle(){
    p.movesAlreadyDone = vector.New(0);
}

func NewChildPegPuzzle(parent *PegPuzzle) *PegPuzzle{
    retVal := new(PegPuzzle);
    retVal.movesAlreadyDone = parent.movesAlreadyDone;
    return retVal
}

func (p *PegPuzzle) doMove(move Move){
    p.movesAlreadyDone.Push(move);
}

func (p *PegPuzzle) printPuzzleInfo(){
    fmt.Printf("-----------START----------------------
");
    fmt.Printf("moves already done: %v
", p.movesAlreadyDone);
    fmt.Printf("------------END-----------------------
");
}

func main() {
    p := new(PegPuzzle);
    cp1 := new(PegPuzzle);
    cp2 := new(PegPuzzle);

    p.InitPegPuzzle();

    cp1 = NewChildPegPuzzle(p);
    cp1.doMove(Move{1,1,2,3});
    cp1.printPuzzleInfo();

    cp2 = NewChildPegPuzzle(p);
    cp2.doMove(Move{3,2,5,1});
    cp2.printPuzzleInfo();
}

Any help will be greatly appreciated. Thanks!

Answer 1

Incidental to the answer, but vector.New has been deleted from recent versions of Go. You need to write

func (p *PegPuzzle) InitPegPuzzle(){
    p.movesAlreadyDone = new (vector.Vector);
}

In your original code, the things you are copying are pointers to vectors. This is just the same as pointers in C. You can call it "by reference" if you like, but they're pointers.

To copy an entire vector, use InsertVector:

func (p *PegPuzzle) InitPegPuzzle(){
    p.movesAlreadyDone = new (vector.Vector);
}

func NewChildPegPuzzle(parent *PegPuzzle) *PegPuzzle{
    retVal := new (PegPuzzle);
    retVal.InitPegPuzzle ();
    retVal.movesAlreadyDone.InsertVector (0, parent.movesAlreadyDone);
    return retVal
}

This gives a complete unique copy.