Correct an error in the value_at function.

[spline3.git] / src / FunctionValues.hs

diff --git a/src/FunctionValues.hs b/src/FunctionValues.hs
index 1d722b12b0f3132d028cbf53d01a9e584be977dd..895f9253a42506398c5594a3bd8b864baa32099a 100644 (file)
--- a/src/FunctionValues.hs
+++ b/src/FunctionValues.hs
@@ -162,18 +162,34 @@ 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.
+--   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 values i j k
-         | i < 0 = 0
-         | j < 0 = 0
-         | k < 0 = 0
-         | xsize <= i = 0
-         | ysize <= j = 0
-         | zsize <= k = 0
-         | otherwise = idx values i j k
+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 values
+    (xsize, ysize, zsize) = dims v3d
 
 
 -- | Given a three-dimensional list of 'Double' and a set of 3D