From: Francis Russell <francis@unchartedbackwaters.co.uk>
Date: Sun, 14 Apr 2013 10:47:06 +0000 (+0100)
Subject: Avoid introducing a sum when negating a product.
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=e1cd8b47d6fae136124780167bbddd4ac8f1e2c1;p=francis%2Flta.git

Avoid introducing a sum when negating a product.
---

diff --git a/LTA/Symbolic.hs b/LTA/Symbolic.hs
index d05f5f6..b52cfc7 100644
--- a/LTA/Symbolic.hs
+++ b/LTA/Symbolic.hs
@@ -187,6 +187,7 @@ instance Num Expr where
   (*) a b = simplify . Product $ empty `addPair` (a, 1) `addPair` (b, 1)
   abs = UnaryFunction Abs
   fromInteger = Literal . fromInteger
+  negate (Product pairSeq) = Product $ transformOverall pairSeq (* (-1))
   negate a = simplify . Sum $ empty `addPair` (a, -1)
   signum = UnaryFunction Signum