From dc6238dbc20af0e3d53a5397b57c4c96b7040180 Mon Sep 17 00:00:00 2001
From: Konstantin Zudov <co@zudov.me>
Date: Sat, 8 Oct 2016 17:26:41 +0300
Subject: [PATCH] Add functional dependencies

---
 src/Control/Monad/Eff/Var.purs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Control/Monad/Eff/Var.purs b/src/Control/Monad/Eff/Var.purs
index 5fc0049..03e35a9 100644
--- a/src/Control/Monad/Eff/Var.purs
+++ b/src/Control/Monad/Eff/Var.purs
@@ -56,18 +56,18 @@ import Data.Functor.Contravariant (class Contravariant, (>$<))
 import Data.Functor.Invariant (class Invariant)
 
 -- | Typeclass for vars that can be read.
-class Gettable (eff :: # !) (var :: * -> *) (a :: *) where
+class Gettable (eff :: # !) (var :: * -> *) (a :: *) | var -> a, var -> eff where
   get :: var a -> Eff eff a
 
 -- | Typeclass for vars that can be written.
-class Settable (eff :: # !) (var :: * -> *) (a :: *) where
+class Settable (eff :: # !) (var :: * -> *) (a :: *) | var -> a, var -> eff where
   set :: var a -> a -> Eff eff Unit
 
 -- | Alias for `set`.
 infixr 2 set as $=
 
 -- | Typeclass for vars that can be updated.
-class Updatable (eff :: # !) (var :: * -> *) (a :: *) where
+class Updatable (eff :: # !) (var :: * -> *) (a :: *) | var -> a, var -> eff where
   update :: var a -> (a -> a) -> Eff eff Unit
 
 -- | Alias for `get`