From 6041c1e2f31b430002745c727c98c6f76e75d1fb Mon Sep 17 00:00:00 2001
From: David Feuer <David.Feuer@gmail.com>
Date: Thu, 29 Oct 2020 19:05:51 -0400
Subject: [PATCH] Add Apply instance for Curried

---
 src/Data/Functor/Day/Curried.hs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/Data/Functor/Day/Curried.hs b/src/Data/Functor/Day/Curried.hs
index 37613b7..117c92b 100644
--- a/src/Data/Functor/Day/Curried.hs
+++ b/src/Data/Functor/Day/Curried.hs
@@ -37,6 +37,7 @@ import Control.Applicative
 import Data.Functor.Adjunction
 import Data.Functor.Day
 import Data.Functor.Identity
+import Data.Functor.Apply
 
 newtype Curried g h a =
   Curried { runCurried :: forall r. g (a -> r) -> h r }
@@ -45,6 +46,14 @@ instance Functor g => Functor (Curried g h) where
   fmap f (Curried g) = Curried (g . fmap (.f))
   {-# INLINE fmap #-}
 
+instance (Functor g, g ~ h) => Apply (Curried g h) where
+  Curried mf <.> Curried ma = Curried (ma . mf . fmap (.))
+  {-# INLINE (<.>) #-}
+#if MIN_VERSION_semigroupoids(5,2,2)
+  liftF2 f (Curried g) (Curried ma) = Curried (ma . g . fmap (\p q -> p . f q))
+  {-# INLINE liftF2 #-}
+#endif
+
 instance (Functor g, g ~ h) => Applicative (Curried g h) where
   pure a = Curried (fmap ($a))
   {-# INLINE pure #-}