gistfile1.hs

type Point = (Double, Double)
type Vector = Point

distance :: Point -> Point -> Double
distance (x1, y1), (x2, y2) = sqrt ((x2-x1)**2 + (y2-y1)**2)

-- Compute the normalized tangent vector from two points
normalizedVector :: Point -> Point -> Vector
normalizedVector (x1, y1) (x2, y1) = (xv / l, yv / l)
    where
      xv = x2 - x1
      yv = y2 - y1
      l = distance (0, 0) (xv, yv)
          
mu :: Double
mu = 6.67428e-11 * 6.0e24

times :: Double -> Vector -> Vector
times v (x, y) = (v*x, v*y)

-- vec is the result of computing normalizedVector on the first two points that
-- were observed (don't fire the rockets before observing!)
delta1 :: Double -> Double -> Vector -> Vector
delta1 r1 r2 vec = (lhs*rhs) `times` vec
    where
      lhs = sqrt (mu / r1)
      rhs = (sqrt (2 * r2 / (r1 + r2))) - 1

-- same note as above
delta2 :: Double -> Double -> Vector -> Vector
delta2 r1 r2 vec = (lhs*rhs) `times` vec
    where
      lhs = sqrt (mu / r2)
      rhs = 1 - (sqrt (2 * r1 / (r1 + r2)))