- = SeqList (OrdList a) (OrdList a)
- | ParList (OrdList a) (OrdList a)
- | OrdObj a
- | NoObj
- deriving ()
-
-mkSeqList a b = SeqList a b
-mkParList a b = ParList a b
-mkEmptyList = NoObj
-mkUnitList = OrdObj
-\end{code}
-
-%------------------------------------------------------------------------
+ = Many (OrdList a) (OrdList a)
+ | One a
+ | None
+
+nilOL :: OrdList a
+isNilOL :: OrdList a -> Bool
+
+unitOL :: a -> OrdList a
+snocOL :: OrdList a -> a -> OrdList a
+consOL :: a -> OrdList a -> OrdList a
+appOL :: OrdList a -> OrdList a -> OrdList a
+concatOL :: [OrdList a] -> OrdList a
+
+nilOL = None
+unitOL as = One as
+snocOL as b = Many as (One b)
+consOL a bs = Many (One a) bs
+concatOL aas = foldr Many None aas
+
+isNilOL None = True
+isNilOL (One _) = False
+isNilOL (Many as bs) = isNilOL as && isNilOL bs
+
+appOL None bs = bs
+appOL as None = as
+appOL as bs = Many as bs
+
+fromOL :: OrdList a -> [a]
+fromOL ol
+ = flat ol []
+ where
+ flat None rest = rest
+ flat (One x) rest = x:rest
+ flat (Many a b) rest = flat a (flat b rest)
+
+toOL :: [a] -> OrdList a
+toOL [] = None
+toOL (x:xs) = Many (One x) (toOL xs)