implemented phase 2

DataModel.hs

@@ -11,8 +11,9 @@ class Freq a where
     frequency :: [ItemSet] -> a -> Frequency
 
 data Item = Item String deriving (Eq, Ord)
+
 instance Show Item where
-    show (Item s) = s --"Item " ++ s
+    show (Item a) = show a
 
 data ItemSet = ItemSet (Set Item) deriving (Eq, Ord)
 
@@ -27,16 +28,23 @@ instance Freq ItemSet where
 
 count :: [ItemSet] -> ItemSet -> Count
 count table (ItemSet set) =
-    length (filter isSuperSet table) where
+    length (filter isSuperset table) where
         isSuperset (ItemSet row) = set `Set.isSubsetOf` row
 
+difference :: ItemSet -> ItemSet -> ItemSet
+difference (ItemSet set1) (ItemSet set2) = ItemSet (Set.difference set1 set2)
+
+empty :: ItemSet
+empty = ItemSet (Set.fromList [])
+
 data Rule = Rule ItemSet ItemSet deriving (Eq)
 
 instance Show Rule where
     show (Rule a b) = show a ++ "-> " ++ show b
 
 instance Freq Rule where
-    frequency table (Rule (ItemSet set1) (ItemSet set2)) = frequency table $ ItemSet (set1 `Set.union` set2)
+    frequency table (Rule (ItemSet set1) (ItemSet set2)) = frequency table $
+        ItemSet (set1 `Set.union` set2)
 
 confidence :: [ItemSet] -> Rule -> Confidence
 confidence table (Rule x y) = frequency table (Rule x y) / frequency table x