X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FFunctionValues.hs;h=e8bdcb8e2d1f294216d38fa24d3b56fcc4cba786;hb=d8bb807e89fbb193b373be111217813d5a4222e9;hp=9fd3c7862516cc404220b66e172201685c18ea35;hpb=1d2e0c4c6e5d766bd3ac6834d9dec298679f7c31;p=spline3.git

diff --git a/src/FunctionValues.hs b/src/FunctionValues.hs
index 9fd3c78..e8bdcb8 100644
--- a/src/FunctionValues.hs
+++ b/src/FunctionValues.hs
@@ -74,8 +74,14 @@ eval f (Product x y) = (eval f x) * (eval f y)
 eval f (Quotient x y) = (eval f x) / (eval f y)
 
 value_at :: [[[Double]]] -> Int -> Int -> Int -> Double
-value_at values i j k =
-    ((values !! k) !! j) !! i
+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
 
 make_values :: [[[Double]]] -> Int -> Int -> Int -> FunctionValues
 make_values values i j k =