working on graph...

[hs-rrdtool.git] / Data / HList / Prelude.hs

diff --git a/Data/HList/Prelude.hs b/Data/HList/Prelude.hs
index dc33147be63c7de93cc58dae3df25d723c3b680b..856c677c67d629b70adea88519a41c863909d988 100644 (file)
--- a/Data/HList/Prelude.hs
+++ b/Data/HList/Prelude.hs
@@ -43,7 +43,9 @@ module Data.HList.Prelude
     , HOccursMany1(..)
     , HOccursOpt(..)
     , HOccurs(..)
-    , HOccursNot(..)
+    , HOccursNot
+
+    , HNoDuplicates
     )
     where
 
@@ -274,6 +276,11 @@ instance HOccursNot e HNil
 instance Fail (TypeFound e) => HOccursNot e (HCons e  l)
 instance HOccursNot e l     => HOccursNot e (HCons e' l)
 
+-- HNoDuplicates
+class    HNoDuplicates l
+instance HNoDuplicates HNil
+instance HOccursNot e l => HNoDuplicates (HCons e l)
+
 {-
 {-
 "Strongly Typed Heterogeneous Collections"