Merge pull request #383 from tek/interpreters-for

add InterpretersFor

ChangeLog.md

@@ -2,6 +2,7 @@
 
 
 ## Unreleased changes
+* Added `InterpretersFor` as a shorthand for interpreters consuming multiple effects
 
 ## 1.4.0.0 (2020-10-31)
 

src/Polysemy/Internal.hs

@@ -34,7 +34,9 @@ module Polysemy.Internal
   , usingSem
   , liftSem
   , hoistSem
+  , Append
   , InterpreterFor
+  , InterpretersFor
   , (.@)
   , (.@@)
   ) where
@@ -579,6 +581,11 @@ runM (Sem m) = m $ \z ->
 {-# INLINE runM #-}
 
 
+type family Append l r where
+  Append (a ': l) r = a ': (Append l r)
+  Append '[] r = r
+
+
 ------------------------------------------------------------------------------
 -- | Type synonym for interpreters that consume an effect without changing the
 -- return value. Offered for user convenience.
@@ -592,6 +599,12 @@ runM (Sem m) = m $ \z ->
 type InterpreterFor e r = ∀ a. Sem (e ': r) a -> Sem r a
 
 
+------------------------------------------------------------------------------
+-- | Variant of 'InterpreterFor' that takes a list of effects.
+-- @since (TODO)
+type InterpretersFor es r = ∀ a. Sem (Append es r) a -> Sem r a
+
+
 ------------------------------------------------------------------------------
 -- | Some interpreters need to be able to lower down to the base monad (often
 -- 'IO') in order to function properly --- some good examples of this are

src/Polysemy/Internal/Bundle.hs

@@ -2,16 +2,16 @@
 
 {-# OPTIONS_HADDOCK not-home #-}
 
-module Polysemy.Internal.Bundle where
+module Polysemy.Internal.Bundle (
+  module Polysemy.Internal.Bundle,
+  Append,
+) where
 
 import Data.Proxy
 import Polysemy
+import Polysemy.Internal (Append)
 import Polysemy.Internal.Union
 
-type family Append l r where
-  Append (a ': l) r = a ': (Append l r)
-  Append '[] r = r
-
 extendMembership :: forall r r' e. ElemOf e r -> ElemOf e (Append r r')
 extendMembership Here = Here
 extendMembership (There e) = There (extendMembership @_ @r' e)