[project @ 2003-12-10 14:15:16 by simonmar]

[ghc-hetmet.git] / ghc / compiler / utils / Bag.lhs

diff --git a/ghc/compiler/utils/Bag.lhs b/ghc/compiler/utils/Bag.lhs
index ed9a540..4ee8b0f 100644 (file)
--- a/ghc/compiler/utils/Bag.lhs
+++ b/ghc/compiler/utils/Bag.lhs
@@ -11,13 +11,15 @@ module Bag (
        mapBag,
        elemBag,
        filterBag, partitionBag, concatBag, foldBag, foldrBag, foldlBag,
-       isEmptyBag, consBag, snocBag,
-       listToBag, bagToList
+       isEmptyBag, isSingletonBag, consBag, snocBag,
+       listToBag, bagToList, 
+       mapBagM, mapAndUnzipBagM
     ) where
 
 #include "HsVersions.h"
 
 import Outputable
+import Util            ( isSingleton )
 import List            ( partition )
 \end{code}
 
@@ -26,10 +28,8 @@ import List          ( partition )
 data Bag a
   = EmptyBag
   | UnitBag    a
-  | TwoBags    (Bag a) (Bag a) -- The ADT guarantees that at least
-                               -- one branch is non-empty
-  | ListBag    [a]             -- The list is non-empty
-  | ListOfBags [Bag a]         -- The list is non-empty
+  | TwoBags    (Bag a) (Bag a) -- INVARIANT: neither branch is empty
+  | ListBag    [a]             -- INVARIANT: the list is non-empty
 
 emptyBag = EmptyBag
 unitBag  = UnitBag
@@ -40,13 +40,13 @@ elemBag x EmptyBag        = False
 elemBag x (UnitBag y)     = x==y
 elemBag x (TwoBags b1 b2) = x `elemBag` b1 || x `elemBag` b2
 elemBag x (ListBag ys)    = any (x ==) ys
-elemBag x (ListOfBags bs) = any (x `elemBag`) bs
 
-unionManyBags [] = EmptyBag
-unionManyBags xs = ListOfBags xs
+unionManyBags :: [Bag a] -> Bag a
+unionManyBags xs = foldr unionBags EmptyBag xs
 
 -- This one is a bit stricter! The bag will get completely evaluated.
 
+unionBags :: Bag a -> Bag a -> Bag a
 unionBags EmptyBag b = b
 unionBags b EmptyBag = b
 unionBags b1 b2      = TwoBags b1 b2
@@ -57,11 +57,14 @@ snocBag :: Bag a -> a -> Bag a
 consBag elt bag = (unitBag elt) `unionBags` bag
 snocBag bag elt = bag `unionBags` (unitBag elt)
 
-isEmptyBag EmptyBag        = True
-isEmptyBag (UnitBag x)     = False
-isEmptyBag (TwoBags b1 b2)  = isEmptyBag b1 && isEmptyBag b2   -- Paranoid, but safe
-isEmptyBag (ListBag xs)     = null xs                          -- Paranoid, but safe
-isEmptyBag (ListOfBags bs)  = all isEmptyBag bs
+isEmptyBag EmptyBag = True
+isEmptyBag other    = False    -- NB invariants
+
+isSingletonBag :: Bag a -> Bool
+isSingletonBag EmptyBag                = False
+isSingletonBag (UnitBag x)     = True
+isSingletonBag (TwoBags b1 b2)  = False                -- Neither is empty
+isSingletonBag (ListBag xs)     = isSingleton xs
 
 filterBag :: (a -> Bool) -> Bag a -> Bag a
 filterBag pred EmptyBag = EmptyBag
@@ -71,17 +74,12 @@ filterBag pred (TwoBags b1 b2) = sat1 `unionBags` sat2
                                 sat1 = filterBag pred b1
                                 sat2 = filterBag pred b2
 filterBag pred (ListBag vs)    = listToBag (filter pred vs)
-filterBag pred (ListOfBags bs) = ListOfBags sats
-                               where
-                                sats = [filterBag pred b | b <- bs]
 
 concatBag :: Bag (Bag a) -> Bag a
-
 concatBag EmptyBag         = EmptyBag
 concatBag (UnitBag b)       = b
-concatBag (TwoBags b1 b2)   = concatBag b1 `TwoBags` concatBag b2
-concatBag (ListBag bs)     = ListOfBags bs
-concatBag (ListOfBags bbs)  = ListOfBags (map concatBag bbs)
+concatBag (TwoBags b1 b2)   = concatBag b1 `unionBags` concatBag b2
+concatBag (ListBag bs)     = unionManyBags bs
 
 partitionBag :: (a -> Bool) -> Bag a -> (Bag a {- Satisfy predictate -},
                                         Bag a {- Don't -})
@@ -94,9 +92,6 @@ partitionBag pred (TwoBags b1 b2) = (sat1 `unionBags` sat2, fail1 `unionBags` fa
 partitionBag pred (ListBag vs)   = (listToBag sats, listToBag fails)
                                  where
                                    (sats,fails) = partition pred vs
-partitionBag pred (ListOfBags bs) = (ListOfBags sats, ListOfBags fails)
-                                 where
-                                   (sats, fails) = unzip [partitionBag pred b | b <- bs]
 
 
 foldBag :: (r -> r -> r)       -- Replace TwoBags with this; should be associative
@@ -110,7 +105,6 @@ foldBag t u e EmptyBag        = e
 foldBag t u e (UnitBag x)     = u x
 foldBag t u e (TwoBags b1 b2) = (foldBag t u e b1) `t` (foldBag t u e b2)
 foldBag t u e (ListBag xs)    = foldr (t.u) e xs
-foldBag t u e (ListOfBags bs) = foldr (\b r -> foldBag e u t b `t` r) e bs
 -}
 
 -- More tail-recursive definition, exploiting associativity of "t"
@@ -118,7 +112,6 @@ foldBag t u e EmptyBag        = e
 foldBag t u e (UnitBag x)     = u x `t` e
 foldBag t u e (TwoBags b1 b2) = foldBag t u (foldBag t u e b2) b1
 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
@@ -128,7 +121,6 @@ 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
 
 foldlBag :: (r -> a -> r) -> r
         -> Bag a
@@ -138,7 +130,6 @@ 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
@@ -146,8 +137,22 @@ mapBag f EmptyBag   = EmptyBag
 mapBag f (UnitBag x)     = UnitBag (f x)
 mapBag f (TwoBags b1 b2) = TwoBags (mapBag f b1) (mapBag f b2) 
 mapBag f (ListBag xs)    = ListBag (map f xs)
-mapBag f (ListOfBags bs) = ListOfBags (map (mapBag f) bs)
 
+mapBagM :: Monad m => (a -> m b) -> Bag a -> m (Bag b)
+mapBagM f EmptyBag       = return EmptyBag
+mapBagM f (UnitBag x)     = do { r <- f x; return (UnitBag r) }
+mapBagM f (TwoBags b1 b2) = do { r1 <- mapBagM f b1; r2 <- mapBagM f b2; return (TwoBags r1 r2) }
+mapBagM f (ListBag    xs) = do { rs <- mapM    f xs; return (ListBag rs) }
+
+mapAndUnzipBagM :: Monad m => (a -> m (b,c)) -> Bag a -> m (Bag b, Bag c)
+mapAndUnzipBagM f EmptyBag       = return (EmptyBag, EmptyBag)
+mapAndUnzipBagM f (UnitBag x)     = do { (r,s) <- f x; return (UnitBag r, UnitBag s) }
+mapAndUnzipBagM f (TwoBags b1 b2) = do { (r1,s1) <- mapAndUnzipBagM f b1
+                                       ; (r2,s2) <- mapAndUnzipBagM f b2
+                                       ; return (TwoBags r1 r2, TwoBags s1 s2) }
+mapAndUnzipBagM f (ListBag    xs) = do { ts <- mapM f xs
+                                       ; let (rs,ss) = unzip ts
+                                       ; return (ListBag rs, ListBag ss) }
 
 listToBag :: [a] -> Bag a
 listToBag [] = EmptyBag
@@ -163,6 +168,4 @@ instance (Outputable a) => Outputable (Bag a) where
     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}