%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[Bags]{@Bag@: an unordered collection with duplicates}
\begin{code}
-#include "HsVersions.h"
-
module Bag (
Bag, -- abstract type
emptyBag, unitBag, unionBags, unionManyBags,
mapBag,
elemBag,
- filterBag, partitionBag, concatBag, foldBag, foldrBag,
+ filterBag, partitionBag, concatBag, foldBag, foldrBag, foldlBag,
isEmptyBag, consBag, snocBag,
listToBag, bagToList
) where
-IMP_Ubiq(){-uitous-}
-IMPORT_1_3(List(partition))
+#include "HsVersions.h"
+
+import Outputable
+import List ( partition )
+\end{code}
-import Outputable --( interpp'SP )
-import Pretty
+\begin{code}
data Bag a
= EmptyBag
| UnitBag a
foldrBag k z (ListBag xs) = foldr k z xs
foldrBag k z (ListOfBags bs) = foldr (\b r -> foldrBag k r b) z bs
+foldlBag :: (r -> a -> r) -> r
+ -> Bag a
+ -> r
+
+foldlBag k z EmptyBag = z
+foldlBag k z (UnitBag x) = k z x
+foldlBag k z (TwoBags b1 b2) = foldlBag k (foldlBag k z b1) b2
+foldlBag k z (ListBag xs) = foldl k z xs
+foldlBag k z (ListOfBags bs) = foldl (\r b -> foldlBag k r b) z bs
+
mapBag :: (a -> b) -> Bag a -> Bag b
mapBag f EmptyBag = EmptyBag
\begin{code}
instance (Outputable a) => Outputable (Bag a) where
- ppr sty EmptyBag = ptext SLIT("emptyBag")
- ppr sty (UnitBag a) = ppr sty a
- ppr sty (TwoBags b1 b2) = hsep [ppr sty b1 <> comma, ppr sty b2]
- ppr sty (ListBag as) = interpp'SP sty as
- ppr sty (ListOfBags bs) = brackets (interpp'SP sty bs)
+ ppr EmptyBag = ptext SLIT("emptyBag")
+ ppr (UnitBag a) = ppr a
+ ppr (TwoBags b1 b2) = hsep [ppr b1 <> comma, ppr b2]
+ ppr (ListBag as) = interpp'SP as
+ ppr (ListOfBags bs) = brackets (interpp'SP bs)
\end{code}