1 files changed, 3 insertions, 0 deletions

diff --git a/haskell/Data/VCDIFF.hs b/haskell/Data/VCDIFF.hs
index fe4cc98..db75fb1 100644
--- a/haskell/Data/VCDIFF.hs
+++ b/haskell/Data/VCDIFF.hs
@@ -273,6 +273,9 @@ data Result x = Result
                   -- is an error code and message indicating what.
     } deriving (Show,Functor)
 
+instance Semigroup x => Semigroup (Result x) where
+    Result x xe <> y = Result (x <> result y) (maybe (resultError y) Just xe)
+
 instance Monoid x => Monoid (Result x) where
     mempty = Result mempty Nothing
     mappend (Result x xe) y = Result (mappend x $ result y) (maybe (resultError y) Just xe)