+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
+
+make_values :: [[[Double]]] -> 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,
+ left = value_at values i (j-1) k,
+ right = value_at values i (j+1) k,
+ down = value_at values i j (k-1),
+ top = value_at values i j (k+1),
+ front_left = value_at values (i-1) (j-1) k,
+ front_right = value_at values (i-1) (j+1) k,
+ front_down =value_at values (i-1) j (k-1),
+ front_top = value_at values (i-1) j (k+1),
+ back_left = value_at values (i+1) (j-1) k,
+ back_right = value_at values (i+1) (j+1) k,
+ back_down = value_at values (i+1) j (k-1),
+ back_top = value_at values (i+1) j (k+1),
+ left_down = value_at values i (j-1) (k-1),
+ left_top = value_at values i (j-1) (k+1),
+ right_top = value_at values i (j+1) (k+1),
+ right_down = value_at values i (j+1) (k-1),
+ front_left_down = value_at values (i-1) (j-1) (k-1),
+ front_left_top = value_at values (i-1) (j-1) (k+1),
+ front_right_down = value_at values (i-1) (j+1) (k-1),
+ front_right_top = value_at values (i-1) (j+1) (k+1),
+ back_left_down = value_at values (i-1) (j-1) (k-1),
+ back_left_top = value_at values (i+1) (j-1) (k+1),
+ back_right_down = value_at values (i+1) (j+1) (k-1),
+ back_right_top = value_at values (i+1) (j+1) (k+1),
+ interior = value_at values i j k }