Remove an unused Misc import.

Switch the 'x' and 'z' axes of cube_at.
Fix calculate_containing_cube_coordinate so that it actually works.

diff --git a/src/Grid.hs b/src/Grid.hs
index b8f1d759e1f268a1e71c33cfa5b7dd3dcb58919a..8ce2430d186870d7e7322d4bf5ff9e381870273c 100644 (file)
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -8,7 +8,6 @@ import Test.QuickCheck (Arbitrary(..), Gen, Positive(..))
 
 import Cube (Cube(Cube), find_containing_tetrahedra)
 import FunctionValues
-import Misc (flatten)
 import Point (Point)
 import Tetrahedron (polynomial)
 import Values (Values3D, dims, empty3d, zoom_shape)
@@ -66,28 +65,30 @@ 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
+    | k >= length (cubes g) = Nothing
+    | j >= length ((cubes g) !! k) = Nothing
+    | i >= length (((cubes g) !! k) !! j) = Nothing
+    | otherwise = Just $ (((cubes g) !! k) !! j) !! i
 
 
 
 --   The first cube along any axis covers (-h/2, h/2). The second
 --   covers (h/2, 3h/2).  The third, (3h/2, 5h/2), and so on.
 --
---   We translate the (x,y,z) coordinates forward by 'h' so that the
+--   We translate the (x,y,z) coordinates forward by 'h/2' so that the
 --   first covers (0, h), the second covers (h, 2h), etc. This makes
 --   it easy to figure out which cube contains the given point.
 calculate_containing_cube_coordinate :: Grid -> Double -> Int
 calculate_containing_cube_coordinate g coord
-    -- Don't use a cube on the boundary if we can help it.
-    | coord == delta && (xsize > 0 && ysize > 0 && zsize > 0) = 1
-    | otherwise = (ceiling ( (coord + delta) / cube_width )) - 1
+    -- Don't use a cube on the boundary if we can help it. This
+    -- returns cube #1 if we would have returned cube #0 and cube #1
+    -- exists.
+    | coord == offset && (xsize > 0 && ysize > 0 && zsize > 0) = 1
+    | otherwise = (ceiling ( (coord + offset) / cube_width )) - 1
     where
       (xsize, ysize, zsize) = dims (function_values g)
-      delta = (h g)
-      cube_width = 2 * delta
+      cube_width = (h g)
+      offset = cube_width / 2
 
 
 -- | Takes a 'Grid', and returns a 'Cube' containing the given 'Point'.