Method that calculates all vectors to draw an arrow

arrow.rb

require "matrix"
require "cmath"

module Arrow

  # Example arrow(6, 4, Vector[10, 10], Vector[100, 100])
  def arrow(arrowhead_length, half_width, foot_vector, tip_vector)
    h = arrowhead_length.to_f * CMath.sqrt(3)
    w = half_width.to_f
    u = (tip_vector - foot_vector) / (tip_vector - foot_vector).norm
    v = Vector[-u[1], u[0]]
    { foot: foot_vector,
      tip: tip_vector - arrowhead_length * u,
      arrowhead: {
        tip: tip_vector,
        left: tip_vector - h * u + w * v,
        right: tip_vector - h * u - w * v }}
  end

  module_function :arrow
end