1 files changed, 31 insertions, 1 deletions
diff --git a/TreeSearch.hs b/TreeSearch.hs
index 938b076..51d65c2 100644
--- a/TreeSearch.hs
+++ b/TreeSearch.hs
@@ -14,6 +14,36 @@ depthFirst loc = case firstChild loc of
     Just x -> Just x
     Nothing -> case next loc of
         Just x -> Just x
+        Nothing -> parentWithNext loc
+  where
+    parentWithNext x =
+        case parent x of
+            Nothing -> Nothing
+            Just x' -> case next x' of
+                Just x' -> Just x'
+                Nothing -> parentWithNext x'
+
+
+findNext :: TreePos Full a -> Maybe (TreePos Full a)
+findNext = depthFirst
+
+
+findPrev :: TreePos Full a -> Maybe (TreePos Full a)
+findPrev loc =
+    case prev loc of
+        Just x -> trans_lastChild x
         Nothing -> case parent loc of
-            Just x -> next x
+            Just x -> Just x
             Nothing -> Nothing
+  where
+    trans_lastChild x =
+        case lastChild x of
+            Nothing -> Just x
+            Just x' -> trans_lastChild x'
+
+
+findParent :: (a -> Bool) -> TreePos Full a -> Maybe (TreePos Full a)
+findParent p loc =
+    if p (label loc)
+        then Just loc
+        else parent loc >>= findParent p