\section[UniqSupply]{The @UniqueSupply@ data type and a (monadic) supply thereof}
\begin{code}
-#include "HsVersions.h"
-
module UniqSupply (
UniqSupply, -- Abstractly
getUnique, getUniques, -- basic ops
- SYN_IE(UniqSM), -- type: unique supply monad
+ UniqSM, -- type: unique supply monad
initUs, thenUs, returnUs, fixUs,
mapUs, mapAndUnzipUs, mapAndUnzip3Us,
thenMaybeUs, mapAccumLUs,
splitUniqSupply
) where
-IMP_Ubiq(){-uitous-}
+#include "HsVersions.h"
import Unique
import Util
-#if __GLASGOW_HASKELL__ == 201
-import PreludeGlaST
-# define WHASH GHCbase.W#
-#elif __GLASGOW_HASKELL__ >= 202
import GlaExts
-import STBase
-# if __GLASGOW_HASKELL__ == 202
+import IOBase ( IO(..), IOResult(..) )
import PrelBase ( Char(..) )
-# endif
-# define WHASH GlaExts.W#
-#else
-import PreludeGlaST
-# define WHASH W#
-#endif
-
-#if __GLASGOW_HASKELL__ >= 209
-import Unsafe ( unsafeInterleaveIO )
-#endif
w2i x = word2Int# x
i2w x = int2Word# x
-- here comes THE MAGIC:
+ -- This is one of the most hammered bits in the whole compiler
mk_supply#
- = unsafe_interleave (
- mk_unique `thenPrimIO` \ uniq ->
- mk_supply# `thenPrimIO` \ s1 ->
- mk_supply# `thenPrimIO` \ s2 ->
- returnPrimIO (MkSplitUniqSupply uniq s1 s2)
+ = unsafeInterleaveIO (
+ mk_unique >>= \ uniq ->
+ mk_supply# >>= \ s1 ->
+ mk_supply# >>= \ s2 ->
+ return (MkSplitUniqSupply uniq s1 s2)
)
- where
---
- -- inlined copy of unsafeInterleavePrimIO;
- -- this is the single-most-hammered bit of code
- -- in the compiler....
- -- Too bad it's not 1.3-portable...
- unsafe_interleave m =
-#if __GLASGOW_HASKELL__ >= 209
- unsafeInterleaveIO m
-#else
- MkST ( \ s ->
- let
- (MkST m') = m
- ST_RET(r, new_s) = m' s
- in
- ST_RET(r, s))
-#endif
-
- mk_unique = _ccall_ genSymZh `thenPrimIO` \ (WHASH u#) ->
- returnPrimIO (I# (w2i (mask# `or#` u#)))
+
+ mk_unique = _ccall_ genSymZh >>= \ (W# u#) ->
+ return (I# (w2i (mask# `or#` u#)))
in
-#if __GLASGOW_HASKELL__ >= 200
- primIOToIO mk_supply# >>= \ s ->
- return s
-#else
- mk_supply# `thenPrimIO` \ s ->
- return s
-#endif
+ mk_supply#
splitUniqSupply (MkSplitUniqSupply _ s1 s2) = (s1, s2)
\end{code}