let bezier = Curve(begin: p.0, control0: c.0, control1: c.1, end: p.1)

let quad = QuadCurve(begin: p.0, control: c, end: p.1)

var points = (Point(canvas.width/4, canvas.height/3),
              Point(canvas.width*3/4, canvas.height/3))
let dy = Vector(x: 0, y: 200)
let bezier = Curve(begin: points.0,
                   control0: points.0 - dy,
                   control1: points.1 + dy,
                   end: points.1)
canvas.add(bezier)

points.0.y *= 2.0
points.1.y *= 2.0
let quad = QuadCurve(begin: points.0, control: canvas.center + dy, end: points.1)

canvas.add(quad)