From 8472f991d02f44895ba7fa4d54c353fd90ac5b97 Mon Sep 17 00:00:00 2001
From: Neil Brown <neil@twistedsquare.com>
Date: Fri, 2 Nov 2007 11:44:04 +0000
Subject: [PATCH] Added error return to the checkInitVar function, and also
 changed it to use the new extended Set implementation, which in turn allowed
 me to fix the bug in the checkInitVar function (defVal is Everything, not the
 empty set)

---
 transformations/RainUsageCheck.hs | 39 +++++++++++++++++--------------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/transformations/RainUsageCheck.hs b/transformations/RainUsageCheck.hs
index f202ad2..4b138ba 100644
--- a/transformations/RainUsageCheck.hs
+++ b/transformations/RainUsageCheck.hs
@@ -22,6 +22,7 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 -- the control-flow graph means that we only need to concentrate on each node that isn't nested.
 module RainUsageCheck where
 
+import Control.Monad.Error
 import Control.Monad.Identity
 import Data.Generics
 import Data.Graph.Inductive
@@ -281,38 +282,42 @@ isSubsetOf (NormalSet a) (NormalSet b) = Set.isSubsetOf a b
 
 
 -- TODO have some sort of error-message return if the check fails or if the code fails
-checkInitVar :: FlowGraph (Maybe Decl, Vars) -> Node -> Bool
-checkInitVar graph startNode = and $ map (checkInitVar' varWrittenBefore) (map readNode (labNodes graph))
+checkInitVar :: FlowGraph (Maybe Decl, Vars) -> Node -> Either String ()
+checkInitVar graph startNode
+  = do vwb <- varWrittenBefore
+       mapM_ (checkInitVar' vwb) (map readNode (labNodes graph))
   where
-    readNode :: (Node, FNode (Maybe Decl, Vars)) -> (Node, Set.Set Var)
-    readNode (n, Node (_,(_,Vars read _ _ _))) = (n,read)
+    readNode :: (Node, FNode (Maybe Decl, Vars)) -> (Node, ExSet Var)
+    readNode (n, Node (_,(_,Vars read _ _ _))) = (n,NormalSet read)
   
-    writeNode :: FNode (Maybe Decl, Vars) -> Set.Set Var
-    writeNode (Node (_,(_,Vars _ _ written _))) = written
+    writeNode :: FNode (Maybe Decl, Vars) -> ExSet Var
+    writeNode (Node (_,(_,Vars _ _ written _))) = NormalSet written
     
     -- Nothing is treated as if were the set of all possible variables (easier than building that set):
-    nodeFunction :: (Node, EdgeLabel) -> Set.Set Var -> Maybe (Set.Set Var) -> Set.Set Var
-    nodeFunction (n,_) inputVal Nothing = Set.union inputVal (maybe Set.empty writeNode (lab graph n))    
-    nodeFunction (n, EEndPar _) inputVal (Just prevAgg) = Set.unions [inputVal,prevAgg,maybe Set.empty writeNode (lab graph n)]
-    nodeFunction (n, _) inputVal (Just prevAgg) = Set.intersection prevAgg $ Set.union inputVal (maybe Set.empty writeNode (lab graph n))
+    nodeFunction :: (Node, EdgeLabel) -> ExSet Var -> Maybe (ExSet Var) -> ExSet Var
+    nodeFunction (n,_) inputVal Nothing = union inputVal (maybe emptySet writeNode (lab graph n))    
+    nodeFunction (n, EEndPar _) inputVal (Just prevAgg) = unions [inputVal,prevAgg,maybe emptySet writeNode (lab graph n)]
+    nodeFunction (n, _) inputVal (Just prevAgg) = intersection prevAgg $ union inputVal (maybe emptySet writeNode (lab graph n))
   
-    graphFuncs :: GraphFuncs Node EdgeLabel (Set.Set Var)
+    graphFuncs :: GraphFuncs Node EdgeLabel (ExSet Var)
     graphFuncs = GF
       {
        nodeFunc = nodeFunction
        ,prevNodes = lpre graph
        ,nextNodes = lsuc graph
-       ,initVal = Set.empty
-       ,defVal = Set.empty
+       ,initVal = emptySet
+       ,defVal = Everything
       }
   
-    varWrittenBefore :: Map.Map Node (Set.Set Var)
+    varWrittenBefore :: Either String (Map.Map Node (ExSet Var))
     varWrittenBefore = flowAlgorithm graphFuncs (nodes graph) startNode
 
-    checkInitVar' :: Map.Map Node (Set.Set Var) -> (Node, Set.Set Var) -> Bool
+    checkInitVar' :: Map.Map Node (ExSet Var) -> (Node, ExSet Var) -> Either String ()
     checkInitVar' writtenMap (n,v)
       = case Map.lookup n writtenMap of
-          Nothing -> False
+          Nothing -> throwError $ "Variable that is read from: " ++ show (lab graph n) ++ " is never written to"
           -- All read vars should be in the previously-written set
-          Just vs -> v `Set.isSubsetOf` vs
+          Just vs -> if v `isSubsetOf` vs then return () else 
+            throwError $ "Variable read from: " ++ show (lab graph n) ++ " is not written to before-hand, sets: " ++ show v ++ " and " ++ show vs
+              ++ " writtenMap: " ++ show writtenMap