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__ == 201
26 #elif __GLASGOW_HASKELL__ >= 202
32 import PreludeGlaST ( MutableVar(..), _MutableArray(..), ST(..) )
35 CHK_Ubiq() -- debugging consistency check
39 data SST_R s r = SST_R r (State# s)
40 type SST s r = State# s -> SST_R s r
45 -- converting to/from ST
47 sstToST :: SST s r -> ST s r
48 stToSST :: ST s r -> SST s r
50 #if __GLASGOW_HASKELL__ >= 200
52 sstToST sst = ST $ \ (S# s) ->
53 case sst s of SST_R r s' -> (r, S# s')
55 stToSST (ST st) = \ s ->
56 case st (S# s) of (r, S# s') -> SST_R r s'
60 = case sst s of SST_R r s' -> (r, S# s')
62 = case st (S# s) of (r, S# s') -> SST_R r s'
65 -- Type of runSST should be builtin ...
66 -- runSST :: forall r. (forall s. SST s r) -> r
68 #if __GLASGOW_HASKELL__ >= 200
69 # define REAL_WORLD RealWorld
70 # define MUT_ARRAY MutableArray
72 # define REAL_WORLD _RealWorld
73 # define MUT_ARRAY _MutableArray
76 runSST :: SST REAL_WORLD r -> r
77 runSST m = case m realWorld# of SST_R r s -> r
79 unsafeInterleaveSST :: SST s r -> SST s r
80 unsafeInterleaveSST m s = SST_R r s -- Duplicates the state!
84 returnSST :: r -> SST s r
85 thenSST :: SST s r -> (r -> State# s -> b) -> State# s -> b
86 thenSST_ :: SST s r -> (State# s -> b) -> State# s -> b
87 fixSST :: (r -> SST s r) -> SST s r
88 {-# INLINE returnSST #-}
89 {-# INLINE thenSST #-}
90 {-# INLINE thenSST_ #-}
93 -- thenSST :: SST s r -> (r -> SST s r') -> SST s r'
94 -- and thenSST :: SST s r -> (r -> FSST s r' err) -> FSST s r' err
97 -- thenSST_ :: SST s r -> SST s r' -> SST s r'
98 -- and thenSST_ :: SST s r -> FSST s r' err -> FSST s r' err
100 thenSST m k s = case m s of { SST_R r s' -> k r s' }
102 thenSST_ m k s = case m s of { SST_R r s' -> k s' }
104 returnSST r s = SST_R r s
109 SST_R loop _ = result
113 \section{FSST: the failable strict state transformer monad}
114 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
118 = FSST_R_OK r (State# s)
119 | FSST_R_Fail err (State# s)
121 type FSST s r err = State# s -> FSST_R s r err
125 failFSST :: err -> FSST s r err
126 fixFSST :: (r -> FSST s r err) -> FSST s r err
127 recoverFSST :: (err -> FSST s r err) -> FSST s r err -> FSST s r err
128 recoverSST :: (err -> SST s r) -> FSST s r err -> SST s r
129 returnFSST :: r -> FSST s r err
130 thenFSST :: FSST s r err -> (r -> FSST s r' err) -> FSST s r' err
131 thenFSST_ :: FSST s r err -> FSST s r' err -> FSST s r' err
132 {-# INLINE failFSST #-}
133 {-# INLINE returnFSST #-}
134 {-# INLINE thenFSST #-}
135 {-# INLINE thenFSST_ #-}
137 thenFSST m k s = case m s of
138 FSST_R_OK r s' -> k r s'
139 FSST_R_Fail err s' -> FSST_R_Fail err s'
141 thenFSST_ m k s = case m s of
142 FSST_R_OK r s' -> k s'
143 FSST_R_Fail err s' -> FSST_R_Fail err s'
145 returnFSST r s = FSST_R_OK r s
147 failFSST err s = FSST_R_Fail err s
149 recoverFSST recovery_fn m s
151 FSST_R_OK r s' -> FSST_R_OK r s'
152 FSST_R_Fail err s' -> recovery_fn err s'
154 recoverSST recovery_fn m s
156 FSST_R_OK r s' -> SST_R r s'
157 FSST_R_Fail err s' -> recovery_fn err s'
162 FSST_R_OK loop _ = result
167 Here we implement mutable variables. ToDo: get rid of the array impl.
170 newMutVarSST :: a -> SST s (MutableVar s a)
171 readMutVarSST :: MutableVar s a -> SST s a
172 writeMutVarSST :: MutableVar s a -> a -> SST s ()
175 = case (newArray# 1# init s#) of { StateAndMutableArray# s2# arr# ->
176 SST_R (MUT_ARRAY vAR_IXS arr#) s2# }
178 vAR_IXS = error "Shouldn't access `bounds' of a MutableVar\n"
180 readMutVarSST (MUT_ARRAY _ var#) s#
181 = case readArray# var# 0# s# of { StateAndPtr# s2# r ->
184 writeMutVarSST (MUT_ARRAY _ var#) val s#
185 = case writeArray# var# 0# val s# of { s2# ->