X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FGrid.hs;h=4b75185ad19b31b4922e5485105b069ec56dba96;hb=58cf11569acb270995d2de924dda03ef526647e2;hp=6d360e2c103d61cc6b41a9cc3873f52db756e169;hpb=6fb9ab6b6068870323e996da931fc04c7710e3e4;p=spline3.git

diff --git a/src/Grid.hs b/src/Grid.hs
index 6d360e2..4b75185 100644
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -29,9 +29,8 @@ 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 == [[[]]] = [[[]]]
@@ -45,3 +44,17 @@ cubes g
       zsize = (length 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