added missing type instances

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

diff --git a/Database/RRDtool/Create.hs b/Database/RRDtool/Create.hs
index a3b51e54171d74e14d1ad822ece4fd8281a0c870..a6a67fca729a31f3a5eefa750c0cc79fff45776f 100644 (file)
--- a/Database/RRDtool/Create.hs
+++ b/Database/RRDtool/Create.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE
+  TypeFamilies,
+  UndecidableInstances
+  #-}
 module Database.RRDtool.Create
     ( DataSource
     , ExternalDSType(..)
@@ -28,6 +32,7 @@ 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
@@ -152,13 +157,14 @@ data ComputedDataSource e
     }
     deriving (Show, Eq, Ord)
 
-instance IsCommonExpr e => DataSource (ComputedDataSource e)
+instance (IsCommonExpr e ~ True) =>
+    DataSource (ComputedDataSource e)
 
 
 dsTest = ComputedDataSource {
            cdsName = "foo"
---       , dsExpr = Previous :<: Const 100
---       , dsExpr = Var "foo" :<: Const 100
+--         , cdsExpr = Previous :<: Const 100
+--         , cdsExpr = Var "foo" :<: Const 100
          , cdsExpr = AverageOf (Const 100 .*. Const 200 .*. HNil)
          }