swift 3.0 数组赋值

   已经不再是简单的赋值了，而且数据拷贝！

func testArray(){    var a = [1,2,3,4];    var b = a;    //a.append(100);    var c = b;    c[1] = 20;    print(a); //[1, 2, 3, 4]    print(b); //[1, 2, 3, 4]    print(c); //[1, 20, 3, 4]}