X-Git-Url: http://git.cielonegro.org/gitweb.cgi?a=blobdiff_plain;f=Database%2FRRDtool%2FCreate.hs;h=5438e044d02b5a746256ed95fe3686a75b29028c;hb=d07e35733d4f0994a12202164c9065aef1fe98f4;hp=cb41c211aa7912d01c6ff04e1a6703c5ca9ad2c1;hpb=b7e8a37aa24e9bda11995613c45187e6e19e0c01;p=hs-rrdtool.git

diff --git a/Database/RRDtool/Create.hs b/Database/RRDtool/Create.hs
index cb41c21..5438e04 100644
--- a/Database/RRDtool/Create.hs
+++ b/Database/RRDtool/Create.hs
@@ -11,7 +11,7 @@ module Database.RRDtool.Create
 
     -- Database.RRDtool.Expression
     , Constant(..)
-    , IsVarName(..)
+    , IsVarName
     , Variable(..)
     , CommonUnaryOp(..)
     , CommonBinaryOp(..)
@@ -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 {