WIP

Author: turion

src/Control/Monad/Bayes/Class.hs

@@ -2,6 +2,8 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# OPTIONS_GHC -Wno-deprecations #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 
 -- |
 -- Module      : Control.Monad.Bayes.Class
@@ -105,6 +107,7 @@ import Statistics.Distribution.Geometric (geometric0)
 import Statistics.Distribution.Normal (normalDistr)
 import Statistics.Distribution.Poisson qualified as Poisson
 import Statistics.Distribution.Uniform (uniformDistr)
+import Control.Monad.Trans (MonadTrans)
 
 -- | Monads that can draw random variables.
 class Monad m => MonadDistribution m where
@@ -407,3 +410,25 @@ instance MonadFactor m => MonadFactor (ContT r m) where
   score = lift . score
 
 instance MonadMeasure m => MonadMeasure (ContT r m)
+
+-- * Utility for deriving MonadDistribution, MonadFactor and MonadMeasure
+
+newtype MonadMeasureTrans (t :: (* -> *) -> * -> *) (m :: * -> *) a = MonadMeasureTrans { getMonadMeasureTrans :: t m a }
+  deriving (Functor, Applicative, Monad)
+
+instance MonadTrans t => MonadTrans (MonadMeasureTrans t) where
+  lift = MonadMeasureTrans . lift
+
+instance (MonadTrans t, MonadDistribution m, Monad (t m)) => MonadDistribution (MonadMeasureTrans t m) where
+  random = lift random
+  uniform = (lift .) . uniform
+  normal = (lift .) . normal
+  gamma = (lift .) . gamma
+  beta = (lift .) . beta
+  bernoulli = lift . bernoulli
+  categorical = lift . categorical
+  logCategorical = lift . logCategorical
+  uniformD = lift . uniformD
+  geometric = lift . geometric
+  poisson = lift . poisson
+  dirichlet = lift . dirichlet