Merge branch 'master' of github.com:isovector/polysemy

src/Polysemy.hs

@@ -9,11 +9,15 @@ module Polysemy
   , runM
   , runFinal
 
+  -- * Type synonyms for user convenience
+  , InterpreterFor
+
   -- * Interoperating With Other Monads
   -- ** Embed
   , Embed (..)
   , embed
   , embedToFinal
+
   -- ** Final
   -- | For advanced uses of 'Final', including creating your own interpreters
   -- that make use of it, see "Polysemy.Final"
@@ -132,11 +136,11 @@ module Polysemy
   , Inspector (..)
   ) where
 
+import Polysemy.Final
 import Polysemy.Internal
 import Polysemy.Internal.Combinators
 import Polysemy.Internal.Forklift
 import Polysemy.Internal.Kind
-import Polysemy.Internal.TH.Effect
 import Polysemy.Internal.Tactics
-import Polysemy.Final
+import Polysemy.Internal.TH.Effect
 

src/Polysemy/Internal.hs

@@ -23,6 +23,7 @@ module Polysemy.Internal
   , usingSem
   , liftSem
   , hoistSem
+  , InterpreterFor
   , (.@)
   , (.@@)
   ) where
@@ -434,6 +435,17 @@ runM (Sem m) = m $ \z ->
       pure $ f $ a <$ s
 {-# INLINE runM #-}
 
+------------------------------------------------------------------------------
+-- | Type synonym for interpreters that consume an effect without changing the 
+-- return value. Offered for user convenience. 
+--
+-- @r@ Is kept polymorphic so it's possible to place constraints upon it:
+--
+-- @
+-- teletypeToIO :: 'Member' (Embed IO) r
+--              => 'InterpreterFor' Teletype r
+-- @
+type InterpreterFor e r = forall a. Sem (e ': r) a -> Sem r a
 
 ------------------------------------------------------------------------------
 -- | Some interpreters need to be able to lower down to the base monad (often