found an edge case where a Data.Map tree map does not work properly for retrieving a successor.

Need to find a better data structure

Hash2Pub/src/CacheEdgeCases.hs

@@ -0,0 +1,29 @@
+import Hash2Pub.FediChord
+import Data.Map.Internal.Debug (showTree)
+import qualified Data.Map.Strict as Map
+
+giebMalCache :: [Integer] -> Map.Map NodeID ()
+giebMalCache = Map.fromList . map (mkCacheEntry . fromInteger)
+  where
+    mkCacheEntry nodeid = (nodeid, ())
+
+testCache1 = giebMalCache [1, -1, 2^50]
+testFirstHalf = giebMalCache [3, 2^254-2, 2^255]
+testOverlap = giebMalCache [2^255+2^254+3, 2, 2^253]
+
+nidLookup m = flip Map.lookup m . fromInteger
+nidLookupLT m = flip Map.lookupLT m . fromInteger
+nidLookupGT m = flip Map.lookupGT m . fromInteger
+
+edgeCase1 :: IO ()
+edgeCase1 = do
+    putStrLn "Let there be a Map with the keys [2^255+2^254+3, 2, 2^253], all keys are NodeIDs mod 2^256."
+    print testOverlap 
+    putStrLn "\nWhile (NodeID 2^255+2^254+3) > (NodeID 2^254 + 14) …"
+    print $ toNodeID (2^255+2^254+3) > toNodeID (2^254+14)
+    putStrLn "… and 2^255+2^254+3 is an element of the map…"
+    print $ Map.member (fromInteger 2^255+2^254+3) testOverlap
+    putStrLn "… looking for an element larger than 2^254 + 14 doesn't yield any."
+    print $ nidLookupGT testOverlap (2^254+14)
+    putStrLn "\nThat's the tree of the map:"
+    putStrLn $ showTree testOverlap