#ifndef COMPILING_GHC
elemBag,
#endif
- filterBag, partitionBag, concatBag, foldBag,
+ filterBag, partitionBag, concatBag, foldBag, foldrBag,
isEmptyBag, consBag, snocBag,
listToBag, bagToList
) where
foldBag t u e (ListBag xs) = foldr (t.u) e xs
foldBag t u e (ListOfBags bs) = foldr (\b r -> foldBag t u r b) e bs
+foldrBag :: (a -> r -> r) -> r
+ -> Bag a
+ -> r
+
+foldrBag k z EmptyBag = z
+foldrBag k z (UnitBag x) = k x z
+foldrBag k z (TwoBags b1 b2) = foldrBag k (foldrBag k z b2) b1
+foldrBag k z (ListBag xs) = foldr k z xs
+foldrBag k z (ListOfBags bs) = foldr (\b r -> foldrBag k r b) z bs
+
mapBag :: (a -> b) -> Bag a -> Bag b
mapBag f EmptyBag = EmptyBag
listToBag vs = ListBag vs
bagToList :: Bag a -> [a]
-bagToList EmptyBag = []
-bagToList (ListBag vs) = vs
-bagToList b = bagToList_append b []
-
- -- (bagToList_append b xs) flattens b and puts xs on the end.
- -- (not exported)
-bagToList_append EmptyBag xs = xs
-bagToList_append (UnitBag x) xs = x:xs
-bagToList_append (TwoBags b1 b2) xs = bagToList_append b1 (bagToList_append b2 xs)
-bagToList_append (ListBag xx) xs = xx++xs
-bagToList_append (ListOfBags bs) xs = foldr bagToList_append xs bs
+bagToList b = foldrBag (:) [] b
\end{code}
\begin{code}
#ifdef COMPILING_GHC
instance (Outputable a) => Outputable (Bag a) where
- ppr sty EmptyBag = ppStr "emptyBag"
+ ppr sty EmptyBag = ppPStr SLIT("emptyBag")
ppr sty (UnitBag a) = ppr sty a
ppr sty (TwoBags b1 b2) = ppCat [ppr sty b1, pp'SP, ppr sty b2]
ppr sty (ListBag as) = interpp'SP sty as