struct Point {
    var x: Int
    var y: Int
}

var a = Point(x: 1, y: 2)
var b = a          // b is a full copy of a
b.x = 99

print("a.x = \(a.x)")   // a.x = 1 (unchanged)
print("b.x = \(b.x)")   // b.x = 99