rwst.icl

   1 implementation module rwst
   2
   3 from Data.Func import $
   4 import Data.Functor
   5 import Data.Monoid
   6 import Control.Monad
   7 import Control.Applicative
   8
   9
  10 Start = "Test"
  11
  12 :: RWST r w s m a = RWST (r s -> m (a, s, w))
  13
  14 runRWST :: (RWST r w s m a) r s -> m (a, s, w)
  15 runRWST (RWST f) r s = f r s
  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`)