1 \section{SST: the strict state transformer monad}
2 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5 #include "HsVersions.h"
8 SST(..), SST_R, FSST(..), FSST_R,
11 thenSST, thenSST_, returnSST,
12 thenFSST, thenFSST_, returnFSST, failFSST,
13 recoverFSST, recoverSST, fixFSST,
15 MutableVar(..), _MutableArray,
16 newMutVarSST, readMutVarSST, writeMutVarSST
19 import PreludeGlaST( MutableVar(..), _MutableArray(..) )
21 CHK_Ubiq() -- debugging consistency check
25 data SST_R s r = SST_R r (State# s)
26 type SST s r = State# s -> SST_R s r
30 -- Type of runSST should be builtin ...
31 -- runSST :: forall r. (forall s. SST s r) -> r
33 _runSST :: SST _RealWorld r -> r
34 _runSST m = case m realWorld# of SST_R r s -> r
37 thenSST :: SST s r -> (r -> State# s -> b) -> State# s -> b
38 {-# INLINE thenSST #-}
40 -- thenSST :: SST s r -> (r -> SST s r') -> SST s r'
41 -- and thenSST :: SST s r -> (r -> FSST s r' err) -> FSST s r' err
43 thenSST m k s = case m s of { SST_R r s' -> k r s' }
45 thenSST_ :: SST s r -> (State# s -> b) -> State# s -> b
46 {-# INLINE thenSST_ #-}
48 -- thenSST_ :: SST s r -> SST s r' -> SST s r'
49 -- and thenSST_ :: SST s r -> FSST s r' err -> FSST s r' err
51 thenSST_ m k s = case m s of { SST_R r s' -> k s' }
53 returnSST :: r -> SST s r
54 {-# INLINE returnSST #-}
55 returnSST r s = SST_R r s
59 \section{FSST: the failable strict state transformer monad}
60 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
63 data FSST_R s r err = FSST_R_OK r (State# s)
64 | FSST_R_Fail err (State# s)
66 type FSST s r err = State# s -> FSST_R s r err
70 thenFSST :: FSST s r err -> (r -> FSST s r' err) -> FSST s r' err
71 {-# INLINE thenFSST #-}
72 thenFSST m k s = case m s of
73 FSST_R_OK r s' -> k r s'
74 FSST_R_Fail err s' -> FSST_R_Fail err s'
76 thenFSST_ :: FSST s r err -> FSST s r' err -> FSST s r' err
77 {-# INLINE thenFSST_ #-}
78 thenFSST_ m k s = case m s of
79 FSST_R_OK r s' -> k s'
80 FSST_R_Fail err s' -> FSST_R_Fail err s'
82 returnFSST :: r -> FSST s r err
83 {-# INLINE returnFSST #-}
84 returnFSST r s = FSST_R_OK r s
86 failFSST :: err -> FSST s r err
87 {-# INLINE failFSST #-}
88 failFSST err s = FSST_R_Fail err s
90 recoverFSST :: (err -> FSST s r err)
93 recoverFSST recovery_fn m s
95 FSST_R_OK r s' -> FSST_R_OK r s'
96 FSST_R_Fail err s' -> recovery_fn err s'
98 recoverSST :: (err -> SST s r)
101 recoverSST recovery_fn m s
103 FSST_R_OK r s' -> SST_R r s'
104 FSST_R_Fail err s' -> recovery_fn err s'
106 fixFSST :: (r -> FSST s r err) -> FSST s r err
110 FSST_R_OK loop _ = result
115 Here we implement mutable variables. ToDo: get rid of the array impl.
118 newMutVarSST :: a -> SST s (MutableVar s a)
120 = case (newArray# 1# init s#) of { StateAndMutableArray# s2# arr# ->
121 SST_R (_MutableArray vAR_IXS arr#) s2# }
123 vAR_IXS = error "Shouldn't access `bounds' of a MutableVar\n"
125 readMutVarSST :: MutableVar s a -> SST s a
126 readMutVarSST (_MutableArray _ var#) s#
127 = case readArray# var# 0# s# of { StateAndPtr# s2# r ->
130 writeMutVarSST :: MutableVar s a -> a -> SST s ()
131 writeMutVarSST (_MutableArray _ var#) val s#
132 = case writeArray# var# 0# val s# of { s2# ->