From: Francis Russell <francis@unchartedbackwaters.co.uk>
Date: Fri, 12 Apr 2013 15:59:34 +0000 (+0100)
Subject: Make extractMultiplier handle single-term Sum.
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=619d8664f918351062c1ba3de0fdf19fd61ec57b;p=francis%2Flta.git

Make extractMultiplier handle single-term Sum.
---

diff --git a/LTA/Symbolic.hs b/LTA/Symbolic.hs
index f29070f..3472fcb 100644
--- a/LTA/Symbolic.hs
+++ b/LTA/Symbolic.hs
@@ -136,7 +136,10 @@ extractMultiplier (Literal literal) = (1, literal)
 extractMultiplier (Product pairSeq) = (expr, coeff) where
   expr = rebuild $ (PairSeq 1 pairSeq' :: PairSeq ProductTag Expr)
   (PairSeq coeff pairSeq') = normalise pairSeq
-extractMultiplier (Sum pairSeq) = (rebuild $ normalise pairSeq, 1)
+extractMultiplier (Sum (PairSeq coeff terms)) =
+  case (coeff, Map.toList terms) of
+    (0, [(a, b)]) -> (a, b)
+    _ -> (rebuild $ normalise (PairSeq coeff terms :: PairSeq SumTag Literal), 1)
 extractMultiplier e = (e, 1)
 
 pow :: Expr -> Expr -> Expr