Correct an error in the value_at function.

[spline3.git] / src / FunctionValues.hs

diff --git a/src/FunctionValues.hs b/src/FunctionValues.hs
index 1fbc044909d4ba28de0b74fcc1c494e754a6829d..895f9253a42506398c5594a3bd8b864baa32099a 100644 (file)
--- a/src/FunctionValues.hs
+++ b/src/FunctionValues.hs
@@ -7,6 +7,7 @@ import Prelude hiding (LT)
 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
@@ -161,22 +162,40 @@ eval f (Quotient x y) = (eval f x) / (eval f y)
 
 -- | 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,