add(a, b)
  a + b

pad(x, y)
  padding y x y x

body
  pad(5px, 10px)

form .button
  padding-left add(10px, 5px)

-opposite-position(pos)
  if pos == top
    bottom
  else if pos == bottom
    top
  else if pos == left
    right
  else if pos == right
    left
  else
    error('Invalid position ' + pos)

opposite(positions)
  for pos in positions
    pos = -opposite-position(pos)
    ret = ret is defined ? ret pos : pos

body
  foo opposite(top)
  foo opposite(left)
  foo opposite(top left)