major rewrite

[hs-rrdtool.git] / Database / RRDtool / Create.hs

diff --git a/Database/RRDtool/Create.hs b/Database/RRDtool/Create.hs
index a3b51e54171d74e14d1ad822ece4fd8281a0c870..5438e044d02b5a746256ed95fe3686a75b29028c 100644 (file)
--- a/Database/RRDtool/Create.hs
+++ b/Database/RRDtool/Create.hs
@@ -28,6 +28,7 @@ import Data.HList
 import Data.Time.Clock
 import Data.Time.Clock.POSIX
 import Database.RRDtool.Expression
+import Types.Data.Bool
 
 
 -- |A single RRD can accept input from several data sources (DS), for
@@ -152,7 +153,8 @@ data ComputedDataSource e
     }
     deriving (Show, Eq, Ord)
 
-instance IsCommonExpr e => DataSource (ComputedDataSource e)
+instance (IsCommonExpr e ~ True) =>
+    DataSource (ComputedDataSource e)
 
 
 dsTest = ComputedDataSource {