Make cube_at either return a cube or error instead of returning a (Maybe Cube).

[spline3.git] / src / Grid.hs

diff --git a/src/Grid.hs b/src/Grid.hs
index 8ce2430d186870d7e7322d4bf5ff9e381870273c..7996319e7a34fc03217c66771582dcd59493275d 100644 (file)
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -4,6 +4,7 @@
 module Grid
 where
 
+import qualified Data.Array.Repa as R
 import Test.QuickCheck (Arbitrary(..), Gen, Positive(..))
 
 import Cube (Cube(Cube), find_containing_tetrahedra)
@@ -12,7 +13,6 @@ import Point (Point)
 import Tetrahedron (polynomial)
 import Values (Values3D, dims, empty3d, zoom_shape)
 
-import qualified Data.Array.Repa as R
 
 -- | 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
@@ -59,17 +59,26 @@ cubes g
 
 -- | 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
+--   position is outside of the grid), it will throw an error.
+cube_at :: Grid -> Int -> Int -> Int -> Cube
 cube_at g i j k
-    | i < 0 = Nothing
-    | j < 0 = Nothing
-    | k < 0 = Nothing
-    | 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
-
+    | i < 0 = error "i < 0 in cube_at"
+    | j < 0 = error "j < 0 in cube_at"
+    | k < 0 = error "k < 0 in cube_at"
+    | otherwise =
+        let zsize = length (cubes g) in
+          if k >= zsize then
+            error "k >= xsize in cube_at"
+          else
+            let ysize = length ((cubes g) !! k) in
+              if j >= ysize then
+                error "j >= ysize in cube_at"
+              else
+                let xsize = length (((cubes g) !! k) !! j) in
+                  if i >= xsize then
+                    error "i >= xsize in cube_at"
+                  else
+                    (((cubes g) !! k) !! j) !! i
 
 
 --   The first cube along any axis covers (-h/2, h/2). The second
@@ -96,9 +105,7 @@ calculate_containing_cube_coordinate g coord
 --   to check every cube.
 find_containing_cube :: Grid -> Point -> Cube
 find_containing_cube g p =
-    case cube_at g i j k of
-      Just c -> c
-      Nothing -> error "No cube contains the given point."
+    cube_at g i j k
     where
       (x, y, z) = p
       i = calculate_containing_cube_coordinate g x
@@ -107,18 +114,19 @@ find_containing_cube g p =
 
 
 {-# INLINE zoom_lookup #-}
-zoom_lookup :: Grid -> a -> (R.DIM3 -> Double)
-zoom_lookup g _ = zoom_result g
+zoom_lookup :: Grid -> Int -> a -> (R.DIM3 -> Double)
+zoom_lookup g scale_factor _ = zoom_result g scale_factor
 
 
 {-# INLINE zoom_result #-}
-zoom_result :: Grid -> R.DIM3 -> Double
-zoom_result g (R.Z R.:. i R.:. j R.:. k) =
+zoom_result :: Grid -> Int -> R.DIM3 -> Double
+zoom_result g scale_factor (R.Z R.:. i R.:. j R.:. k) =
   f p
   where
-    i' = fromIntegral i
-    j' = fromIntegral j
-    k' = fromIntegral k
+    sf = fromIntegral scale_factor
+    i' = fromIntegral i / sf
+    j' = fromIntegral j / sf
+    k' = fromIntegral k / sf
     p  = (i', j', k') :: Point
     c = find_containing_cube g p
     t = head (find_containing_tetrahedra c p)
@@ -129,7 +137,7 @@ zoom :: Grid -> Int -> Values3D
 zoom g scale_factor
     | xsize == 0 || ysize == 0 || zsize == 0 = empty3d
     | otherwise =
-        R.force $ R.traverse arr transExtent (zoom_lookup g)
+        R.force $ R.traverse arr transExtent (zoom_lookup g scale_factor)
           where
             arr = function_values g
             (xsize, ysize, zsize) = dims arr