1 files changed, 36 insertions, 0 deletions
diff --git a/ProofGraph.hs b/ProofGraph.hs
new file mode 100644
index 0000000..0cd2e7e
--- /dev/null
+++ b/ProofGraph.hs
@@ -0,0 +1,36 @@
+module ProofGraph (
+	Node(..),
+	Graph(..),
+
+	empty,
+	insert,
+	delete,
+	union
+	) where
+
+import Data.Set( Set )
+import qualified Data.Set as Set
+
+
+
+data Node a = Node { contents :: a
+                   , successors :: Set (Node a) } deriving (Eq, Ord, Show)
+
+data Graph a = Graph { nodes :: Set (Node a) } deriving (Show)
+
+
+
+empty :: Graph a
+empty = Graph Set.empty
+
+
+insert :: Ord a => Node a -> Graph a -> Graph a
+insert node graph = Graph (Set.insert node (nodes graph))
+
+
+delete :: Ord a => Node a -> Graph a -> Graph a
+delete node graph = Graph (Set.delete node (nodes graph))
+
+
+union :: Ord a => Set (Node a) -> Graph a -> Graph a
+union nodeSet graph = Graph (Set.union nodeSet (nodes graph))