def setup
  background(220)
  v = createVector(10.0, 20.0)
  rotated_v = P5Vector.rotate(v, HALF_PI)
  text(rotated_v.toString, 10, 20, 70)
end

def setup
  @angle = 0
end

def draw
  background(240)
  v0 = createVector(50, 50)
  v1 = createVector(50, 0)
  drawArrow(v0, P5Vector.rotate(v1, @angle), 'black')
  @angle += 0.01
end

# draw an arrow for a vector at a given base position
def drawArrow(base, vec, myColor)
  push do
    stroke(myColor)
    strokeWeight(3)
    fill(myColor)
    translate(base.x, base.y)
    line(0, 0, vec.x, vec.y)
    rotate(vec.heading)
    arrowSize = 7
    translate(vec.mag - arrowSize, 0)
    triangle(0, arrowSize / 2, 0, -arrowSize / 2, arrowSize, 0)
  end
end