[project @ 2002-05-09 13:16:29 by simonmar]
[packages/random.git] / System / Mem / StableName.hs
1 -----------------------------------------------------------------------------
2 -- |
3 -- Module : System.Mem.StableName
4 -- Copyright : (c) The University of Glasgow 2001
5 -- License : BSD-style (see the file libraries/base/LICENSE)
6 --
7 -- Maintainer : libraries@haskell.org
8 -- Stability : experimental
9 -- Portability : non-portable
10 --
11 -- Giving an object a stable (GC-invariant) name.
12 --
13 -----------------------------------------------------------------------------
14
15 module System.Mem.StableName
16 ( StableName {-a-} -- abstract, instance of Eq
17 , makeStableName -- :: a -> IO (StableName a)
18 , hashStableName -- :: StableName a -> Int
19 ) where
20
21 import Prelude
22
23 import Data.Dynamic
24
25 #ifdef __GLASGOW_HASKELL__
26 import GHC.IOBase ( IO(..) )
27 import GHC.Base ( Int(..), StableName#, makeStableName#
28 , eqStableName#, stableNameToInt# )
29
30 -----------------------------------------------------------------------------
31 -- Stable Names
32
33 data StableName a = StableName (StableName# a)
34
35 makeStableName :: a -> IO (StableName a)
36 #if defined(__PARALLEL_HASKELL__)
37 makeStableName a =
38 error "makeStableName not implemented in parallel Haskell"
39 #else
40 makeStableName a = IO $ \ s ->
41 case makeStableName# a s of (# s', sn #) -> (# s', StableName sn #)
42 #endif
43
44 hashStableName :: StableName a -> Int
45 #if defined(__PARALLEL_HASKELL__)
46 hashStableName (StableName sn) =
47 error "hashStableName not implemented in parallel Haskell"
48 #else
49 hashStableName (StableName sn) = I# (stableNameToInt# sn)
50 #endif
51
52 instance Eq (StableName a) where
53 #if defined(__PARALLEL_HASKELL__)
54 (StableName sn1) == (StableName sn2) =
55 error "eqStableName not implemented in parallel Haskell"
56 #else
57 (StableName sn1) == (StableName sn2) =
58 case eqStableName# sn1 sn2 of
59 0# -> False
60 _ -> True
61 #endif
62
63 #endif /* __GLASGOW_HASKELL__ */
64
65 #include "Dynamic.h"
66 INSTANCE_TYPEABLE1(StableName,stableNameTc,"StableName")