Add a find_containing_cubes function to the Grid module.

[spline3.git] / src / Grid.hs

diff --git a/src/Grid.hs b/src/Grid.hs
index 6d360e2c103d61cc6b41a9cc3873f52db756e169..1a436acdc00d9276ceb1e25b7080355577822bf3 100644 (file)
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -6,6 +6,10 @@ where
 
 import Cube (Cube(Cube))
 import FunctionValues
+import Misc (flatten)
+import Point (Point)
+import ThreeDimensional (contains_point)
+
 
 -- | Our problem is defined on a Grid. The grid size is given by the
 --   positive number h. The function values are the values of the
@@ -29,9 +33,8 @@ empty_grid :: Grid
 empty_grid = Grid 1 [[[]]]
 
 
-
--- This is how we do a 'for' loop in Haskell.
--- No, seriously.
+-- | Returns a three-dimensional list of cubes centered on the grid
+--   points of g with the appropriate 'FunctionValues'.
 cubes :: Grid -> [[[Cube]]]
 cubes g
     | fvs == [[[]]] = [[[]]]
@@ -43,5 +46,29 @@ cubes g
     where
       fvs = function_values g
       zsize = (length fvs) - 1
-      ysize = (length $ head fvs) - 1
-      xsize = (length $ head $ head fvs) - 1
+      ysize = length (head fvs) - 1
+      xsize = length (head $ head fvs) - 1
+
+
+-- | Takes a grid and a position as an argument and returns the cube
+--   centered on that position. If there is no cube there (i.e. the
+--   position is outside of the grid), it will return 'Nothing'.
+cube_at :: Grid -> Int -> Int -> Int -> Maybe Cube
+cube_at g i j k
+    | i < 0 = Nothing
+    | j < 0 = Nothing
+    | k < 0 = Nothing
+    | i >= length (cubes g) = Nothing
+    | j >= length ((cubes g) !! i) = Nothing
+    | k >= length (((cubes g) !! i) !! j) = Nothing
+    | otherwise = Just $ (((cubes g) !! i) !! j) !! k
+
+
+-- | Takes a 'Grid', and returns all 'Cube's belonging to it that
+--   contain the given 'Point'.
+find_containing_cubes :: Grid -> Point -> [Cube]
+find_containing_cubes g p =
+    filter contains_our_point all_cubes
+    where
+      all_cubes = flatten $ cubes g
+      contains_our_point = flip contains_point p