From 803a7f027541067b6ee30a805114a88b934a33aa Mon Sep 17 00:00:00 2001
From: Francis Russell <francis@unchartedbackwaters.co.uk>
Date: Wed, 19 Sep 2012 16:32:18 +0100
Subject: [PATCH] Validate degree of spatial derivatives.

---
 src/TopLevel.hs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/TopLevel.hs b/src/TopLevel.hs
index 8cd8ea2..9d1e0f5 100644
--- a/src/TopLevel.hs
+++ b/src/TopLevel.hs
@@ -275,7 +275,11 @@ validateExpression ofl (PositionComponent i) = do
   indexExists ofl i
   indexIsType ofl i SpatialIndex
 
-validateExpression ofl (SpatialDerivative e d _) = do
+validateExpression ofl (SpatialDerivative e d n) = do
   validateExpression ofl e
+  isFunction ofl e
   indexExists ofl d
+  if n > 0
+    then validationSuccess
+    else validationFailure $ "Degree of derivative of " ++ show e ++ " must be greater than 0."
   indexIsType ofl d SpatialIndex
-- 
2.47.3