import Test.QuickCheck (Arbitrary(..), choose)
import Cardinal
+import Values (Values3D, dims, idx)
-- | The FunctionValues type represents the value of our function f at
-- the 27 points surrounding (and including) the center of a
-- | Takes a three-dimensional list of 'Double' and a set of 3D
-- coordinates (i,j,k), and returns the value at (i,j,k) in the
--- supplied list. If there is no such value, zero is returned.
-value_at :: [[[Double]]] -> Int -> Int -> Int -> Double
-value_at values i j k
- | i < 0 = 0
- | j < 0 = 0
- | k < 0 = 0
- | length values <= k = 0
- | length (values !! k) <= j = 0
- | length ((values !! k) !! j) <= i = 0
- | otherwise = ((values !! k) !! j) !! i
+-- supplied list. If there is no such value, we choose a nearby
+-- point and use its value.
+--
+-- Examples:
+--
+-- >>> value_at Examples.trilinear 0 0 0
+-- 1.0
+--
+-- >>> value_at Examples.trilinear (-1) 0 0
+-- 1.0
+--
+-- >>> value_at Examples.trilinear 0 0 4
+-- 1.0
+--
+-- >>> value_at Examples.trilinear 1 3 0
+-- 4.0
+--
+value_at :: Values3D -> Int -> Int -> Int -> Double
+value_at v3d i j k
+ | i < 0 = value_at v3d 0 j k
+ | j < 0 = value_at v3d i 0 k
+ | k < 0 = value_at v3d i j 0
+ | xsize <= i = value_at v3d (xsize - 1) j k
+ | ysize <= j = value_at v3d i (ysize - 1) k
+ | zsize <= k = value_at v3d i j (zsize - 1)
+ | otherwise = idx v3d i j k
+ where
+ (xsize, ysize, zsize) = dims v3d
-- | Given a three-dimensional list of 'Double' and a set of 3D
-- coordinates (i,j,k), constructs and returns the 'FunctionValues'
-- object centered at (i,j,k)
-make_values :: [[[Double]]] -> Int -> Int -> Int -> FunctionValues
+make_values :: Values3D -> Int -> Int -> Int -> FunctionValues
make_values values i j k =
empty_values { front = value_at values (i-1) j k,
back = value_at values (i+1) j k,