1 files changed, 5 insertions, 1 deletions
diff --git a/Types.hs b/Types.hs
index ce986c7..bbf296f 100644
--- a/Types.hs
+++ b/Types.hs
@@ -22,6 +22,7 @@ import JSON
 
 import qualified Data.Text as T
 import Data.Time.Clock.POSIX
+import qualified Data.Semigroup as Sem
 
 -- | Things that the developer sees.
 data Seen = Seen
@@ -194,9 +195,12 @@ newtype ElapsedTime = ElapsedTime Double
 mkElapsedTime :: POSIXTime -> POSIXTime -> ElapsedTime
 mkElapsedTime start end = ElapsedTime $ fromRational $ toRational (end - start)
 
+instance Sem.Semigroup ElapsedTime where
+	ElapsedTime a <> ElapsedTime b = ElapsedTime (a+b)
+
 instance Monoid ElapsedTime where
 	mempty = ElapsedTime 0
-	mappend (ElapsedTime a) (ElapsedTime b) = ElapsedTime (a+b)
+	mappend = (Sem.<>)
 
 instance DataSize ElapsedTime where
 	dataSize _ = 16 -- 128 bit Double