Control-Monad-Eff-Class.purs

module Control.Monad.Eff.Class 
  ( MonadEff
  , liftEff
  ) where

import Prelude

import Control.Monad.Eff

-- | The `MonadEff` class captures those monads which support native effects.
-- |
-- | Instances are provided for `Eff` itself, and the standard monad transformers.
-- |
-- | `liftEff` can be used in any appropriate monad transformer stack to lift an action
-- | of type `Eff eff a` into the monad.
-- |
-- | Note that `MonadEff` is parameterized by the row of effects, so type inference can be
-- | tricky. It is generally recommended to either work with a polymorphic row of effects,
-- | or a concrete, closed row of effects such as `(trace :: Trace)`.
class (Monad m) <= MonadEff eff m where
  liftEff :: forall a. Eff eff a -> m a

instance monadEffEff :: MonadEff eff (Eff eff) where
  liftEff = id