[project @ 2004-12-14 12:44:52 by simonmar]

[ghc-base.git] / Data / Typeable.hs

diff --git a/Data/Typeable.hs b/Data/Typeable.hs
index ff2b304..d7fd008 100644 (file)
--- a/Data/Typeable.hs
+++ b/Data/Typeable.hs
@@ -9,15 +9,24 @@
 -- Stability   :  experimental
 -- Portability :  portable
 --
--- The Typeable class reifies types to some extent by associating type
+-- The 'Typeable' class reifies types to some extent by associating type
 -- representations to types. These type representations can be compared,
 -- and one can in turn define a type-safe cast operation. To this end,
 -- an unsafe cast is guarded by a test for type (representation)
--- equivalence. The module Data.Dynamic uses Typeable for an
--- implementation of dynamics. The module Data.Generics uses Typeable
+-- equivalence. The module "Data.Dynamic" uses Typeable for an
+-- implementation of dynamics. The module "Data.Generics" uses Typeable
 -- and type-safe cast (but not dynamics) to support the \"Scrap your
 -- boilerplate\" style of generic programming.
 --
+-- Note, only relevant if you use dynamic linking. If you have a program
+-- that is statically linked with Data.Typeable, and then dynamically link
+-- a program that also uses Data.Typeable, you'll get two copies of the module.
+-- That's fine, but behind the scenes, the module uses a mutable variable to
+-- allocate unique Ids to type constructors.  So in the situation described,
+-- there'll be two separate Id allocators, which aren't comparable to each other.
+-- This can lead to chaos.  (It's a bug that we will fix.)  None of
+-- this matters if you aren't using dynamic linking.
+--
 -----------------------------------------------------------------------------
 
 module Data.Typeable
@@ -39,13 +48,13 @@ module Data.Typeable
        mkTyConApp,     -- :: TyCon   -> [TypeRep] -> TypeRep
        mkAppTy,        -- :: TypeRep -> TypeRep   -> TypeRep
        mkFunTy,        -- :: TypeRep -> TypeRep   -> TypeRep
-       splitTyConApp,  -- :: TypeRep -> (TyCon, [TypeRep])
-       funResultTy,    -- :: TypeRep -> TypeRep   -> Maybe TypeRep
 
        -- * Observation of type representations
-       typerepTyCon,   -- :: TypeRep -> TyCon
-       typerepArgs,    -- :: TypeRep -> [TypeRep]
-       tyconString,    -- :: TyCon   -> String
+       splitTyConApp,  -- :: TypeRep -> (TyCon, [TypeRep])
+       funResultTy,    -- :: TypeRep -> TypeRep   -> Maybe TypeRep
+       typeRepTyCon,   -- :: TypeRep -> TyCon
+       typeRepArgs,    -- :: TypeRep -> [TypeRep]
+       tyConString,    -- :: TyCon   -> String
 
        -- * The other Typeable classes
        -- | /Note:/ The general instances are provided for GHC only.
@@ -211,16 +220,16 @@ mkTyCon str = TyCon (mkTyConKey str) str
 ----------------- Observation ---------------------
 
 -- | Observe the type constructor of a type representation
-typerepTyCon :: TypeRep -> TyCon
-typerepTyCon (TypeRep _ tc _) = tc
+typeRepTyCon :: TypeRep -> TyCon
+typeRepTyCon (TypeRep _ tc _) = tc
 
 -- | Observe the argument types of a type representation
-typerepArgs :: TypeRep -> [TypeRep]
-typerepArgs (TypeRep _ _ args) = args
+typeRepArgs :: TypeRep -> [TypeRep]
+typeRepArgs (TypeRep _ _ args) = args
 
 -- | Observe string encoding of a type representation
-tyconString :: TyCon   -> String
-tyconString  (TyCon _ str) = str
+tyConString :: TyCon   -> String
+tyConString  (TyCon _ str) = str
 
 ----------------- Showing TypeReps --------------------
 
@@ -478,15 +487,15 @@ instance Typeable6 (,,,,,) where
   typeOf6 tu = mkTyConApp tup6Tc []
 
 tup7Tc :: TyCon
-tup7Tc = mkTyCon ",,,,,"
+tup7Tc = mkTyCon ",,,,,,"
 
 instance Typeable7 (,,,,,,) where
   typeOf7 tu = mkTyConApp tup7Tc []
 
 #endif /* __NHC__ */
-INSTANCE_TYPEABLE1(Ptr,ptrTc,"Foreign.Ptr.Ptr")
-INSTANCE_TYPEABLE1(StablePtr,stableptrTc,"Foreign.StablePtr.StablePtr")
-INSTANCE_TYPEABLE1(IORef,iorefTc,"Data.IORef.IORef")
+INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
+INSTANCE_TYPEABLE1(StablePtr,stableptrTc,"StablePtr")
+INSTANCE_TYPEABLE1(IORef,iorefTc,"IORef")
 
 -------------------------------------------------------
 --
@@ -518,6 +527,7 @@ INSTANCE_TYPEABLE0(TypeRep,typeRepTc,"TypeRep")
 
 #ifdef __GLASGOW_HASKELL__
 INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
+INSTANCE_TYPEABLE1(MVar,mvarTc,"MVar" )
 #endif
 
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