RWST.icl

   1 implementation module RWST
   2
   3 import StdTuple
   4
   5 from Data.Func import $
   6 import Data.Void
   7 import Data.Functor.Identity
   8 import Data.Functor
   9 import Data.Monoid
  10 import Control.Monad
  11 import Control.Applicative
  12
  13
  14 // The RWST monad transformer
  15 :: RWST r w s m a = RWST (r s -> m (a, s, w))
  16
  17 instance Functor (RWST r w s m) | Monad m & Monoid w where
  18         fmap f m = liftM f m
  19
  20 instance Applicative (RWST r w s m) | Monad m & Monoid w where
  21     pure a = RWST \_ s->pure (a, s, mempty)
  22         (<*>) mf mx = ap mf mx
  23
  24 instance Monad (RWST r w s m) | Monad m & Monoid w where
  25         bind m k = RWST \r s->runRWST m r s
  26                 >>= \(a, s`, w)->runRWST (k a) r s`
  27                 >>= \(b, s``,w`)->pure (b, s``, mappend w w`)
  28
  29 runRWST :: (RWST r w s m a) r s -> m (a, s, w)
  30 runRWST (RWST f) r s = f r s
  31
  32 evalRWST :: (RWST r w s m a) r s -> m (a, w) | Monad m
  33 evalRWST m r s = runRWST m r s >>= \(a, _, w)->pure (a, w)
  34
  35 execRWST :: (RWST r w s m a) r s -> m (s, w) | Monad m
  36 execRWST m r s = runRWST m r s >>= \(_, s`, w)->pure (s, w)
  37
  38 mapRWST :: ((m (a, s, w)) -> n (b, s, w`)) (RWST r w s m a) -> RWST r w` s n b
  39 mapRWST f m = RWST \r s->f $ runRWST m r s
  40
  41 withRWST :: (r` -> s -> (r, s)) (RWST r w s m a) -> RWST r` w s m a
  42 withRWST f m = RWST \r s->uncurry (runRWST m) $ f r s
  43
  44 // Reader operations
  45 ask :: RWST r w s m r | Monoid w & Monad m
  46 ask = RWST \r s->pure (r, s, mempty)
  47
  48 local :: (r -> r) (RWST r w s m a) -> RWST r w s m a | Monoid w & Monad m
  49 local f m = RWST \r s->runRWST m (f r) s
  50
  51 asks :: (r -> a) -> RWST r w s m a | Monoid w & Monad m
  52 asks f = ask >>= \r->pure $ f r
  53
  54 // Writer operations
  55 tell :: w -> RWST r w s m Void | Monoid w & Monad m
  56 tell w = RWST \_ s->pure (Void, s,w)
  57
  58 listen :: (RWST r w s m a) -> RWST r w s m (a, w) | Monoid w & Monad m
  59 listen m = RWST \r s->runRWST m r s >>= \(a, s`, w)->pure ((a, w), s`, w)
  60
  61 pass :: (RWST r w s m (a, w -> w)) -> RWST r w s m a | Monoid w & Monad m
  62 pass m = RWST \r s->runRWST m r s >>= \((a, f), s`, w)->pure (a, s`, f w)
  63
  64 listens :: (w -> b) (RWST r w s m a) -> RWST r w s m (a, b)| Monoid w & Monad m
  65 listens f m = listen m >>= \(a, w)->pure (a, f w)
  66
  67 censor :: (w -> w) (RWST r w s m a) -> RWST r w s m a | Monoid w & Monad m
  68 censor f m = pass $ m >>= \a->pure (a, f)
  69
  70 // State operation
  71 get :: RWST r w s m s | Monoid w & Monad m
  72 get = RWST \_ s->pure (s, s, mempty)
  73
  74 put :: s -> RWST r w s m Void | Monoid w & Monad m
  75 put s = RWST \_ _->pure (Void, s, mempty)
  76
  77 modify :: (s -> s) -> RWST r w s m Void | Monoid w & Monad m
  78 modify f = get >>= \s->put $ f s
  79
  80 gets :: (s -> a) -> RWST r w s m a | Monoid w & Monad m
  81 gets f = get >>= \s->pure $ f s
  82
  83 // Lifting other operations
  84 liftCallCC :: ((((a,s,w) -> m (b,s,w)) -> m (a,s,w)) -> m (a,s,w)) ((a -> RWST r w s m b) -> RWST r w s m a) -> RWST r w s m a | Monoid w
  85 liftCallCC callCC f = RWST \r s->callCC
  86         \c->runRWST (f $ \a->RWST \_ _->c (a, s, mempty)) r s
  87
  88 liftCallCC` :: ((((a,s,w) -> m (b,s,w)) -> m (a,s,w)) -> m (a,s,w)) ((a -> RWST r w s m b) -> RWST r w s m a) -> RWST r w s m a | Monoid w
  89 liftCallCC` callCC f = RWST \r s->callCC
  90         \c->runRWST (f $ \a->RWST \_ s`->c (a, s`, mempty)) r s
  91
  92 liftCatch :: ((m (a,s,w)) (e -> m (a,s,w)) -> m (a,s,w)) (RWST l w s m a) (e -> RWST l w s m a) -> RWST l w s m a
  93 liftCatch catchError m h = RWST \r s->catchError
  94         (runRWST m r s) (\e->runRWST (h e) r s)