What is this called?

Affine.hs

-- | Ordered affine spaces are made of points and vectors.
--
-- - Vectors can be added, that's the 'Semigroup' superclass.
-- - Points can be translated along vectors using @('.+')@.
-- - Given two ordered points @i <= j@, @j '.-.?' i@ finds a vector @n@
--   such that @i + n = j@.
--
-- In other words, we only require the existence of "positive" vectors.
--
-- __Laws:__
--
-- @
--               (x '.+' v) '.+' w  =  x '.+' (v '<>' w)
-- x '<=' y  ==>  x '.+' (y '.-.' x)  =  y
--              (x '.+' v) '.-.' x  =  x
-- @
class (Ord (Point v), Semigroup v) => Affine v where
  type Point v

  infixr 6 .+

  -- | Translation.
  (.+) :: Point v -> v -> Point v

  -- | Vector between two points.
  -- @j .-.? i@ must be defined ('Just') if @i <= j@,
  (.-.?) :: Point v -> Point v -> Maybe v