Fix panic when running "ghc -H"; trac #3364

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

diff --git a/compiler/utils/Bag.lhs b/compiler/utils/Bag.lhs
index 481dedf..b2be2c3 100644 (file)
--- a/compiler/utils/Bag.lhs
+++ b/compiler/utils/Bag.lhs
@@ -11,16 +11,19 @@ module Bag (
 
         emptyBag, unitBag, unionBags, unionManyBags,
         mapBag,
-        elemBag,
+        elemBag, lengthBag,
         filterBag, partitionBag, concatBag, foldBag, foldrBag, foldlBag,
         isEmptyBag, isSingletonBag, consBag, snocBag, anyBag,
         listToBag, bagToList,
         mapBagM, mapAndUnzipBagM
     ) where
 
+#include "Typeable.h"
+
 import Outputable
-import Util ( isSingleton )
+import Util
 
+import Data.Data
 import Data.List ( partition )
 
 infixr 3 `consBag`
@@ -41,6 +44,12 @@ emptyBag = EmptyBag
 unitBag :: a -> Bag a
 unitBag  = UnitBag
 
+lengthBag :: Bag a -> Int
+lengthBag EmptyBag        = 0
+lengthBag (UnitBag {})    = 1
+lengthBag (TwoBags b1 b2) = lengthBag b1 + lengthBag b2
+lengthBag (ListBag xs)    = length xs
+
 elemBag :: Eq a => a -> Bag a -> Bool
 elemBag _ EmptyBag        = False
 elemBag x (UnitBag y)     = x == y
@@ -182,4 +191,12 @@ bagToList b = foldrBag (:) [] b
 \begin{code}
 instance (Outputable a) => Outputable (Bag a) where
     ppr bag = braces (pprWithCommas ppr (bagToList bag))
+
+INSTANCE_TYPEABLE1(Bag,bagTc,"Bag")
+
+instance Data a => Data (Bag a) where
+  gfoldl k z b = z listToBag `k` bagToList b -- traverse abstract type abstractly
+  toConstr _   = abstractConstr $ "Bag("++show (typeOf (undefined::a))++")"
+  gunfold _ _  = error "gunfold"
+  dataTypeOf _ = mkNoRepType "Bag"
 \end{code}