Fix the definition of cube_at; it had the 'x' and 'z' axes flipped.

[spline3.git] / src / Cube.hs

diff --git a/src/Cube.hs b/src/Cube.hs
index d0276c8277062ee3c0a360e6a228dbb32bd1b40d..301128116eb0f9127c5e5012fb5b0a4c9f5552df 100644 (file)
--- a/src/Cube.hs
+++ b/src/Cube.hs
@@ -38,8 +38,7 @@ instance Show Cube where
 empty_cube :: Cube
 empty_cube = Cube empty_grid 0 0 0 0
 
--- TODO: The paper considers 'i' to be the front/back direction,
--- whereas I have it in the left/right direction.
+
 instance Gridded Cube where
     back c = cube_at (grid c) ((i c) + 1) (j c) (k c)
     down c = cube_at (grid c) (i c) (j c) ((k c) - 1)
@@ -105,9 +104,9 @@ instance ThreeDimensional Cube where
              i' = fromIntegral (i c) :: Double
              j' = fromIntegral (j c) :: Double
              k' = fromIntegral (k c) :: Double
-             x = (delta * i')
-             y = (delta * j')
-             z = (delta * k')
+             x = delta * i'
+             y = delta * j'
+             z = delta * k'
 
     contains_point c p
         | (x_coord p) < (xmin c) = False
@@ -146,10 +145,14 @@ instance Fractional Cube where
 
     fromRational q = empty_cube { datum = fromRational q }
 
+-- | Constructs a cube, switching the x and z axes.
 reverse_cube :: Grid -> Int -> Int -> Int -> Double -> Cube
-reverse_cube g k' j' i' datum' = Cube g i' j' k' datum'
+reverse_cube g k' j' i' = Cube g i' j' k'
 
 
+-- | Return the cube corresponding to the grid point i,j,k. The list
+--   of cubes is stored as [z][y][x] but we'll be requesting it by
+--   [x][y][z] so we flip the indices in the last line.
 cube_at :: Grid -> Int -> Int -> Int -> Cube
 cube_at g i' j' k'
         | i' >= length (function_values g) = Cube g i' j' k' 0
@@ -159,17 +162,29 @@ cube_at g i' j' k'
         | k' >= length (((function_values g) !! i') !! j') = Cube g i' j' k' 0
         | k' < 0                                          = Cube g i' j' k' 0
         | otherwise =
-            Cube g i' j' k' ((((function_values g) !! i') !! j') !! k')
+            (((cubes g) !! k') !! j') !! i'
+
 
 -- These next three functions basically form a 'for' loop, looping
 -- through the xs, ys, and zs in that order.
-cubes_from_values :: Grid -> Int -> Int -> [Double] -> [Cube]
-cubes_from_values g i' j' vals =
-    zipWith (reverse_cube g i' j') [0..] vals
-
-cubes_from_planes :: Grid -> Int -> [[Double]] -> [[Cube]]
-cubes_from_planes g i' planes =
-    zipWith (cubes_from_values g i') [0..] planes
 
+-- | The cubes_from_values function will return a function that takes
+--   a list of values and returns a list of cubes. It could just as
+--   well be written to take the values as a parameter; the omission
+--   of the last parameter is known as an eta reduce.
+cubes_from_values :: Grid -> Int -> Int -> ([Double] -> [Cube])
+cubes_from_values g i' j' =
+    zipWith (reverse_cube g i' j') [0..]
+
+-- | The cubes_from_planes function will return a function that takes
+--   a list of planes and returns a list of cubes. It could just as
+--   well be written to take the planes as a parameter; the omission
+--   of the last parameter is known as an eta reduce.
+cubes_from_planes :: Grid -> Int -> ([[Double]] -> [[Cube]])
+cubes_from_planes g i' =
+    zipWith (cubes_from_values g i') [0..]
+
+-- | Takes a grid as an argument, and returns a three-dimensional list
+--   of cubes centered on its grid points.
 cubes :: Grid -> [[[Cube]]]
 cubes g = zipWith (cubes_from_planes g) [0..] (function_values g)