1 \section{SST: the strict state transformer monad}
2 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5 #include "HsVersions.h"
8 SYN_IE(SST), SST_R, SYN_IE(FSST), FSST_R,
10 runSST, sstToST, stToSST,
11 thenSST, thenSST_, returnSST, fixSST,
12 thenFSST, thenFSST_, returnFSST, failFSST,
13 recoverFSST, recoverSST, fixFSST,
16 newMutVarSST, readMutVarSST, writeMutVarSST
17 #if __GLASGOW_HASKELL__ >= 200
20 , MutableVar(..), _MutableArray
24 #if __GLASGOW_HASKELL__ >= 200
27 import PreludeGlaST ( MutableVar(..), _MutableArray(..), ST(..) )
30 CHK_Ubiq() -- debugging consistency check
34 data SST_R s r = SST_R r (State# s)
35 type SST s r = State# s -> SST_R s r
40 -- converting to/from ST
42 sstToST :: SST s r -> ST s r
43 stToSST :: ST s r -> SST s r
45 #if __GLASGOW_HASKELL__ >= 200
47 sstToST sst = ST $ \ (S# s) ->
48 case sst s of SST_R r s' -> (r, S# s')
50 stToSST (ST st) = \ s ->
51 case st (S# s) of (r, S# s') -> SST_R r s'
55 = case sst s of SST_R r s' -> (r, S# s')
57 = case st (S# s) of (r, S# s') -> SST_R r s'
60 -- Type of runSST should be builtin ...
61 -- runSST :: forall r. (forall s. SST s r) -> r
63 #if __GLASGOW_HASKELL__ >= 200
64 # define REAL_WORLD RealWorld
65 # define MUT_ARRAY MutableArray
67 # define REAL_WORLD _RealWorld
68 # define MUT_ARRAY _MutableArray
71 runSST :: SST REAL_WORLD r -> r
72 runSST m = case m realWorld# of SST_R r s -> r
74 unsafeInterleaveSST :: SST s r -> SST s r
75 unsafeInterleaveSST m s = SST_R r s -- Duplicates the state!
79 returnSST :: r -> SST s r
80 thenSST :: SST s r -> (r -> State# s -> b) -> State# s -> b
81 thenSST_ :: SST s r -> (State# s -> b) -> State# s -> b
82 fixSST :: (r -> SST s r) -> SST s r
83 {-# INLINE returnSST #-}
84 {-# INLINE thenSST #-}
85 {-# INLINE thenSST_ #-}
88 -- thenSST :: SST s r -> (r -> SST s r') -> SST s r'
89 -- and thenSST :: SST s r -> (r -> FSST s r' err) -> FSST s r' err
92 -- thenSST_ :: SST s r -> SST s r' -> SST s r'
93 -- and thenSST_ :: SST s r -> FSST s r' err -> FSST s r' err
95 thenSST m k s = case m s of { SST_R r s' -> k r s' }
97 thenSST_ m k s = case m s of { SST_R r s' -> k s' }
99 returnSST r s = SST_R r s
104 SST_R loop _ = result
108 \section{FSST: the failable strict state transformer monad}
109 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
113 = FSST_R_OK r (State# s)
114 | FSST_R_Fail err (State# s)
116 type FSST s r err = State# s -> FSST_R s r err
120 failFSST :: err -> FSST s r err
121 fixFSST :: (r -> FSST s r err) -> FSST s r err
122 recoverFSST :: (err -> FSST s r err) -> FSST s r err -> FSST s r err
123 recoverSST :: (err -> SST s r) -> FSST s r err -> SST s r
124 returnFSST :: r -> FSST s r err
125 thenFSST :: FSST s r err -> (r -> FSST s r' err) -> FSST s r' err
126 thenFSST_ :: FSST s r err -> FSST s r' err -> FSST s r' err
127 {-# INLINE failFSST #-}
128 {-# INLINE returnFSST #-}
129 {-# INLINE thenFSST #-}
130 {-# INLINE thenFSST_ #-}
132 thenFSST m k s = case m s of
133 FSST_R_OK r s' -> k r s'
134 FSST_R_Fail err s' -> FSST_R_Fail err s'
136 thenFSST_ m k s = case m s of
137 FSST_R_OK r s' -> k s'
138 FSST_R_Fail err s' -> FSST_R_Fail err s'
140 returnFSST r s = FSST_R_OK r s
142 failFSST err s = FSST_R_Fail err s
144 recoverFSST recovery_fn m s
146 FSST_R_OK r s' -> FSST_R_OK r s'
147 FSST_R_Fail err s' -> recovery_fn err s'
149 recoverSST recovery_fn m s
151 FSST_R_OK r s' -> SST_R r s'
152 FSST_R_Fail err s' -> recovery_fn err s'
157 FSST_R_OK loop _ = result
162 Here we implement mutable variables. ToDo: get rid of the array impl.
165 newMutVarSST :: a -> SST s (MutableVar s a)
166 readMutVarSST :: MutableVar s a -> SST s a
167 writeMutVarSST :: MutableVar s a -> a -> SST s ()
170 = case (newArray# 1# init s#) of { StateAndMutableArray# s2# arr# ->
171 SST_R (MUT_ARRAY vAR_IXS arr#) s2# }
173 vAR_IXS = error "Shouldn't access `bounds' of a MutableVar\n"
175 readMutVarSST (MUT_ARRAY _ var#) s#
176 = case readArray# var# 0# s# of { StateAndPtr# s2# r ->
179 writeMutVarSST (MUT_ARRAY _ var#) val s#
180 = case writeArray# var# 0# val s# of { s2# ->