src/Grid.hs

   1 -- | The Grid module just contains the Grid type and two constructors
   2 --   for it. We hide the main Grid constructor because we don't want
   3 --   to allow instantiation of a grid with h <= 0.
   4 module Grid (empty_grid,
   5              function_values,
   6              Grid,
   7              h,
   8              make_grid)
   9 where
  10
  11 -- | Our problem is defined on a Grid. The grid size is given by the
  12 --   positive number h. The function values are the values of the
  13 --   function at the grid points, which are distance h from one
  14 --   another in each direction (x,y,z).
  15 data Grid = Grid { h :: Double, -- MUST BE GREATER THAN ZERO!
  16                    function_values :: [[[Double]]] }
  17           deriving (Eq, Show)
  18
  19
  20 -- | The constructor that we want people to use. If we're passed a
  21 --   non-positive grid size, we throw an error.
  22 make_grid :: Double -> [[[Double]]] -> Grid
  23 make_grid grid_size values
  24     | grid_size <= 0 = error "grid size must be positive"
  25     | otherwise = Grid grid_size values
  26
  27
  28 -- | Creates an empty grid with grid size 1.
  29 empty_grid :: Grid
  30 empty_grid = Grid 1 [[[]]]