From 6a0d7f5c434c3564d0119befb6799fd77581050a Mon Sep 17 00:00:00 2001
From: Paul Oliver <contact@pauloliver.dev>
Date: Fri, 3 Jan 2025 11:01:20 -0800
Subject: Initial

---
 ch10_10.4-i.hs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 ch10_10.4-i.hs

(limited to 'ch10_10.4-i.hs')

diff --git a/ch10_10.4-i.hs b/ch10_10.4-i.hs
new file mode 100644
index 0000000..3e7606a
--- /dev/null
+++ b/ch10_10.4-i.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+
+-- Exercise 10.4-i
+-- Write a promoted functor instance for tuples.
+
+import Data.Kind (Type)
+
+type Exp a = a -> Type
+
+type family Eval (e :: Exp a) :: a
+
+data Map :: (a -> Exp b) -> f a -> Exp (f b)
+
+type instance Eval (Map f '(a, b)) = '(a, Eval (f b))
-- 
cgit v1.2.1