diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 0.8.1.0
+
+- Add `(Fcf.Combinators.>>=)`
+- Resolve warnings about deprecated `TypeInType`
+
 # 0.8.0.1
 
 - Bump upper bounds for GHC 9.0
@@ -33,7 +38,7 @@
 
 # 0.6.0.0
 
-- Add `Fcf.Utils.Case` and `(Fcf.Combinators.>>=)` (thanks to TheMatten)
+- Add `Fcf.Utils.Case` (thanks to TheMatten)
 - Deprecate `Fcf.Bool.Guarded`
 - GHC 8.8 compatibility
 
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright Li-yao Xia (c) 2018
+Copyright Li-yao Xia (c) 2018-2024
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the “Software”), to deal in
diff --git a/first-class-families.cabal b/first-class-families.cabal
--- a/first-class-families.cabal
+++ b/first-class-families.cabal
@@ -1,5 +1,5 @@
 name:                first-class-families
-version:             0.8.0.1
+version:             0.8.1.0
 synopsis:
   First-class type families
 description:
@@ -11,13 +11,16 @@
 license-file:        LICENSE
 author:              Li-yao Xia
 maintainer:          lysxia@gmail.com
-copyright:           2018 Li-yao Xia
+copyright:           2018-2024 Li-yao Xia
 category:            Other
 build-type:          Simple
 extra-source-files:  README.md, CHANGELOG.md
 cabal-version:       >=1.10
 tested-with:
-  GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.1, GHC == 8.10.1, GHC == 9.0.1
+  GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5,
+  GHC == 8.8.1, GHC == 8.10.1, GHC == 9.0.1, GHC == 9.2.1,
+  GHC == 9.2.8, GHC == 9.4.8, GHC == 9.6.4, GHC == 9.8.2,
+  GHC == 9.10.1
 
 library
   hs-source-dirs:      src
@@ -40,10 +43,11 @@
     Fcf.Class.Ord
     Fcf.Utils
   build-depends:
-    -- This upper bound is conservative.
-    base >= 4.9 && < 4.16
+    base >= 4.9 && < 5
   ghc-options:         -Wall
   default-language:    Haskell2010
+  if impl(ghc < 8.6)
+    default-extensions: TypeInType
 
 test-suite fcf-test
   type:                exitcode-stdio-1.0
diff --git a/src/Fcf.hs b/src/Fcf.hs
--- a/src/Fcf.hs
+++ b/src/Fcf.hs
@@ -27,7 +27,6 @@
 -- >     DataKinds,
 -- >     PolyKinds,
 -- >     TypeFamilies,
--- >     TypeInType,
 -- >     TypeOperators,
 -- >     UndecidableInstances #-}
 
diff --git a/src/Fcf/Class/Bifunctor.hs b/src/Fcf/Class/Bifunctor.hs
--- a/src/Fcf/Class/Bifunctor.hs
+++ b/src/Fcf/Class/Bifunctor.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -21,16 +20,21 @@
 import Fcf.Combinators (Pure)
 
 -- $setup
+-- >>> :set -XGADTs
 -- >>> import Fcf.Core (Eval)
 -- >>> import Fcf.Combinators (Flip)
 -- >>> import Fcf.Data.Nat (Nat, type (+), type (-))
 -- >>> import Fcf.Data.Symbol (Symbol)
+-- >>> import Numeric.Natural (Natural)
 
 -- | Type-level 'Data.Bifunctor.bimap'.
 --
--- >>> :kind! Eval (Bimap ((+) 1) (Flip (-) 1) '(2, 4))
--- Eval (Bimap ((+) 1) (Flip (-) 1) '(2, 4)) :: (Nat, Nat)
--- = '(3, 3)
+-- === __Example__
+--
+-- >>> data Example where Ex :: a -> Example  -- Hide the type of examples to avoid brittleness in different GHC versions
+-- >>> :kind! Ex (Eval (Bimap ((+) 1) (Flip (-) 1) '(2, 4)) :: (Natural, Natural))
+-- Ex (Eval (Bimap ((+) 1) (Flip (-) 1) '(2, 4)) :: (Natural, Natural)) :: Example
+-- = Ex '(3, 3)
 data Bimap :: (a -> Exp a') -> (b -> Exp b') -> f a b -> Exp (f a' b')
 
 -- (,)
@@ -47,7 +51,7 @@
 -- === __Example__
 --
 -- >>> :kind! Eval (First ((+) 1) '(3,"a"))
--- Eval (First ((+) 1) '(3,"a")) :: (Nat, Symbol)
+-- Eval (First ((+) 1) '(3,"a")) :: (Natural, Symbol)
 -- = '(4, "a")
 data First :: (a -> Exp b) -> f a c -> Exp (f b c)
 type instance Eval (First f x) = Eval (Bimap f Pure x)
@@ -60,7 +64,7 @@
 -- === __Example__
 --
 -- >>> :kind! Eval (Second ((+) 1) '("a",3))
--- Eval (Second ((+) 1) '("a",3)) :: (Symbol, Nat)
+-- Eval (Second ((+) 1) '("a",3)) :: (Symbol, Natural)
 -- = '("a", 4)
 data Second :: (c -> Exp d) -> f a c -> Exp (f a d)
 type instance Eval (Second g x) = Eval (Bimap Pure g x)
diff --git a/src/Fcf/Class/Foldable.hs b/src/Fcf/Class/Foldable.hs
--- a/src/Fcf/Class/Foldable.hs
+++ b/src/Fcf/Class/Foldable.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -56,8 +55,12 @@
 import Fcf.Data.Nat (Nat, type (+))
 
 -- $setup
--- >>> import Fcf.Combinators (Flip)
+-- >>> import Fcf.Core (Eval)
+-- >>> import Fcf.Combinators (Flip, Pure)
 -- >>> import Fcf.Class.Ord (type (<))
+-- >>> import Fcf.Class.Monoid (type (.<>))
+-- >>> import Fcf.Data.Nat (type (+))
+-- >>> import Numeric.Natural
 
 -- | Type-level 'Data.Foldable.foldMap'.
 data FoldMap :: (a -> Exp m) -> t a -> Exp m
@@ -87,9 +90,9 @@
 --
 -- ==== __Example__
 --
--- >>> :kind! FoldMapDefault_ Pure '[ 'EQ, 'LT, 'GT ]
--- FoldMapDefault_ Pure '[ 'EQ, 'LT, 'GT ] :: Ordering
--- = 'LT
+-- >>> :kind! FoldMapDefault_ Pure [EQ, LT, GT]
+-- FoldMapDefault_ Pure [EQ, LT, GT] :: Ordering
+-- = LT
 type FoldMapDefault_ f xs = Eval (Foldr (Bicomap f Pure (.<>)) MEmpty xs)
 
 -- | Default implementation of 'Foldr'.
@@ -105,17 +108,17 @@
 --
 -- ==== __Example__
 --
--- >>> :kind! FoldrDefault_ (.<>) 'EQ '[ 'EQ, 'LT, 'GT ]
--- FoldrDefault_ (.<>) 'EQ '[ 'EQ, 'LT, 'GT ] :: Ordering
--- = 'LT
+-- >>> :kind! FoldrDefault_ (.<>) EQ [EQ, LT, GT]
+-- FoldrDefault_ (.<>) EQ [EQ, LT, GT] :: Ordering
+-- = LT
 type FoldrDefault_ f y xs = Eval (UnEndo (Eval (FoldMap (Pure1 'Endo <=< Pure1 f) xs)) y)
 
 -- | Right fold.
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Foldr (+) 0 '[1, 2, 3, 4])
--- Eval (Foldr (+) 0 '[1, 2, 3, 4]) :: Nat
+-- >>> :kind! Eval (Foldr (+) 0 [1, 2, 3, 4])
+-- Eval (Foldr (+) 0 [1, 2, 3, 4]) :: Natural
 -- = 10
 data Foldr :: (a -> b -> Exp b) -> b -> t a -> Exp b
 
@@ -137,13 +140,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (And '[ 'True, 'True])
--- Eval (And '[ 'True, 'True]) :: Bool
--- = 'True
+-- >>> :kind! Eval (And [True, True])
+-- Eval (And [True, True]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (And '[ 'True, 'True, 'False])
--- Eval (And '[ 'True, 'True, 'False]) :: Bool
--- = 'False
+-- >>> :kind! Eval (And [True, True, False])
+-- Eval (And [True, True, False]) :: Bool
+-- = False
 data And :: t Bool -> Exp Bool
 type instance Eval (And lst) = Eval (Foldr (&&) 'True lst)
 
@@ -153,13 +156,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (All (Flip (<) 6) '[0,1,2,3,4,5])
--- Eval (All (Flip (<) 6) '[0,1,2,3,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval (All (Flip (<) 6) [0,1,2,3,4,5])
+-- Eval (All (Flip (<) 6) [0,1,2,3,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (All (Flip (<) 5) '[0,1,2,3,4,5])
--- Eval (All (Flip (<) 5) '[0,1,2,3,4,5]) :: Bool
--- = 'False
+-- >>> :kind! Eval (All (Flip (<) 5) [0,1,2,3,4,5])
+-- Eval (All (Flip (<) 5) [0,1,2,3,4,5]) :: Bool
+-- = False
 data All :: (a -> Exp Bool) -> t a -> Exp Bool
 type instance Eval (All p lst) = Eval (Foldr (Bicomap p Pure (&&)) 'True lst)
 
@@ -168,13 +171,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Or '[ 'True, 'True])
--- Eval (Or '[ 'True, 'True]) :: Bool
--- = 'True
+-- >>> :kind! Eval (Or [True, True])
+-- Eval (Or [True, True]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (Or '[ 'False, 'False])
--- Eval (Or '[ 'False, 'False]) :: Bool
--- = 'False
+-- >>> :kind! Eval (Or [False, False])
+-- Eval (Or [False, False]) :: Bool
+-- = False
 data Or :: t Bool -> Exp Bool
 type instance Eval (Or lst) = Eval (Foldr (||) 'False lst)
 
@@ -186,13 +189,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Any (Flip (<) 5) '[0,1,2,3,4,5])
--- Eval (Any (Flip (<) 5) '[0,1,2,3,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval (Any (Flip (<) 5) [0,1,2,3,4,5])
+-- Eval (Any (Flip (<) 5) [0,1,2,3,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (Any (Flip (<) 0) '[0,1,2,3,4,5])
--- Eval (Any (Flip (<) 0) '[0,1,2,3,4,5]) :: Bool
--- = 'False
+-- >>> :kind! Eval (Any (Flip (<) 0) [0,1,2,3,4,5])
+-- Eval (Any (Flip (<) 0) [0,1,2,3,4,5]) :: Bool
+-- = False
 data Any :: (a -> Exp Bool) -> t a -> Exp Bool
 type instance Eval (Any p lst) = Eval (Foldr (Bicomap p Pure (||)) 'False lst)
 
@@ -202,7 +205,7 @@
 -- === __Example__
 --
 -- >>> :kind! Eval (Sum '[1,2,3])
--- Eval (Sum '[1,2,3]) :: Nat
+-- Eval (Sum '[1,2,3]) :: Natural
 -- = 6
 data Sum :: t Nat -> Exp Nat
 type instance Eval (Sum ns) = Eval (Foldr (+) 0 ns)
@@ -216,12 +219,12 @@
 --
 -- > Concat :: [[a]] -> Exp [a]
 --
--- >>> :kind! Eval (Concat ( '[ '[1,2], '[3,4], '[5,6]]))
--- Eval (Concat ( '[ '[1,2], '[3,4], '[5,6]])) :: [Nat]
--- = '[1, 2, 3, 4, 5, 6]
--- >>> :kind! Eval (Concat ( '[ '[Int, Maybe Int], '[Maybe String, Either Double Int]]))
--- Eval (Concat ( '[ '[Int, Maybe Int], '[Maybe String, Either Double Int]])) :: [*]
--- = '[Int, Maybe Int, Maybe String, Either Double Int]
+-- >>> :kind! Eval (Concat ([[1,2], [3,4], [5,6]]))
+-- Eval (Concat ([[1,2], [3,4], [5,6]])) :: [Natural]
+-- = [1, 2, 3, 4, 5, 6]
+-- >>> :kind! Eval (Concat ([[Int, Maybe Int], [Maybe String, Either Double Int]]))
+-- Eval (Concat ([[Int, Maybe Int], [Maybe String, Either Double Int]])) :: [*]
+-- = [Int, Maybe Int, Maybe [Char], Either Double Int]
 --
 data Concat :: t m -> Exp m
 type instance Eval (Concat xs) = Eval (FoldMap Pure xs)
diff --git a/src/Fcf/Class/Functor.hs b/src/Fcf/Class/Functor.hs
--- a/src/Fcf/Class/Functor.hs
+++ b/src/Fcf/Class/Functor.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -14,7 +13,7 @@
 import Fcf.Core (Exp, Eval)
 
 -- $setup
--- >>> :set -XUndecidableInstances -XTypeInType
+-- >>> :set -XUndecidableInstances -XDataKinds -XPolyKinds -XGADTs
 -- >>> import Fcf.Core (Eval, Exp)
 -- >>> import Fcf.Data.Nat
 -- >>> import qualified GHC.TypeLits as TL
@@ -26,11 +25,12 @@
 --
 -- === __Example__
 --
+-- >>> data Example where Ex :: a -> Example  -- Hide the type of examples to avoid brittleness in different GHC versions
 -- >>> data AddMul :: Nat -> Nat -> Exp Nat
 -- >>> type instance Eval (AddMul x y) = (x TL.+ y) TL.* (x TL.+ y)
--- >>> :kind! Eval (Map (AddMul 2) '[0, 1, 2, 3, 4])
--- Eval (Map (AddMul 2) '[0, 1, 2, 3, 4]) :: [Nat]
--- = '[4, 9, 16, 25, 36]
+-- >>> :kind! Ex (Eval (Map (AddMul 2) '[0, 1, 2, 3, 4]) :: [Nat])
+-- Ex (Eval (Map (AddMul 2) '[0, 1, 2, 3, 4]) :: [Nat]) :: Example
+-- = Ex [4, 9, 16, 25, 36]
 data Map :: (a -> Exp b) -> f a -> Exp (f b)
 
 -- | Synonym of 'Map' to avoid name clashes.
diff --git a/src/Fcf/Class/Monoid.hs b/src/Fcf/Class/Monoid.hs
--- a/src/Fcf/Class/Monoid.hs
+++ b/src/Fcf/Class/Monoid.hs
@@ -3,7 +3,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -30,6 +29,7 @@
 
 -- $setup
 -- >>> import GHC.TypeLits (Nat)
+-- >>> import Numeric.Natural (Natural)
 
 -- | Type-level semigroup composition @('Data.Semigroup.<>')@.
 --
@@ -87,17 +87,17 @@
 --
 -- === __Examples__
 --
--- >>> :kind! 'LT <> MEmpty
--- 'LT <> MEmpty :: Ordering
--- = 'LT
+-- >>> :kind! LT <> MEmpty
+-- LT <> MEmpty :: Ordering
+-- = LT
 --
--- >>> :kind! MEmpty <> '( 'EQ, '[1, 2])
--- MEmpty <> '( 'EQ, '[1, 2]) :: (Ordering, [Nat])
--- = '( 'EQ, '[1, 2])
+-- >>> :kind! MEmpty <> '(EQ, [1, 2])
+-- MEmpty <> '(EQ, [1, 2]) :: (Ordering, [Natural])
+-- = '(EQ, [1, 2])
 --
--- >>> :kind! '( 'GT, 'Just '()) <> MEmpty
--- '( 'GT, 'Just '()) <> MEmpty :: (Ordering, Maybe ())
--- = '( 'GT, 'Just '())
+-- >>> :kind! '(GT, Just '()) <> MEmpty
+-- '(GT, Just '()) <> MEmpty :: (Ordering, Maybe ())
+-- = '(GT, Just '())
 type family MEmpty :: a
 
 -- (,)
diff --git a/src/Fcf/Class/Monoid/Types.hs b/src/Fcf/Class/Monoid/Types.hs
--- a/src/Fcf/Class/Monoid/Types.hs
+++ b/src/Fcf/Class/Monoid/Types.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
diff --git a/src/Fcf/Class/Ord.hs b/src/Fcf/Class/Ord.hs
--- a/src/Fcf/Class/Ord.hs
+++ b/src/Fcf/Class/Ord.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -38,15 +37,15 @@
 --
 -- >>> :kind! Eval (Compare "a" "b")
 -- Eval (Compare "a" "b") :: Ordering
--- = 'LT
+-- = LT
 --
 -- >>> :kind! Eval (Compare '[1, 2, 3] '[1, 2, 3])
 -- Eval (Compare '[1, 2, 3] '[1, 2, 3]) :: Ordering
--- = 'EQ
+-- = EQ
 --
 -- >>> :kind! Eval (Compare '[1, 3] '[1, 2])
 -- Eval (Compare '[1, 3] '[1, 2]) :: Ordering
--- = 'GT
+-- = GT
 data Compare :: a -> a -> Exp Ordering
 
 -- (,)
@@ -109,7 +108,7 @@
 --
 -- >>> :kind! Eval ("b" <= "a")
 -- Eval ("b" <= "a") :: Bool
--- = 'False
+-- = False
 data (<=) :: a -> a -> Exp Bool
 type instance Eval ((<=) a b) = Compare a b ~/= 'GT
 
@@ -119,7 +118,7 @@
 --
 -- >>> :kind! Eval ("b" >= "a")
 -- Eval ("b" >= "a") :: Bool
--- = 'True
+-- = True
 data (>=) :: a -> a -> Exp Bool
 type instance Eval ((>=) a b) = Compare a b ~/= 'LT
 
@@ -129,7 +128,7 @@
 --
 -- >>> :kind! Eval ("a" < "b")
 -- Eval ("a" < "b") :: Bool
--- = 'True
+-- = True
 data (<) :: a -> a -> Exp Bool
 type instance Eval ((<) a b) = Compare a b ~== 'LT
 
@@ -139,6 +138,6 @@
 --
 -- >>> :kind! Eval ("b" > "a")
 -- Eval ("b" > "a") :: Bool
--- = 'True
+-- = True
 data (>) :: a -> a -> Exp Bool
 type instance Eval ((>) a b) = Compare a b ~== 'GT
diff --git a/src/Fcf/Combinators.hs b/src/Fcf/Combinators.hs
--- a/src/Fcf/Combinators.hs
+++ b/src/Fcf/Combinators.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -15,6 +14,7 @@
   , Pure2
   , Pure3
   , type (=<<)
+  , type (>>=)
   , type (<=<)
   , LiftM
   , LiftM2
diff --git a/src/Fcf/Core.hs b/src/Fcf/Core.hs
--- a/src/Fcf/Core.hs
+++ b/src/Fcf/Core.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators #-}
 
 -- | The 'Eval' family.
diff --git a/src/Fcf/Data/Bool.hs b/src/Fcf/Data/Bool.hs
--- a/src/Fcf/Data/Bool.hs
+++ b/src/Fcf/Data/Bool.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
diff --git a/src/Fcf/Data/Common.hs b/src/Fcf/Data/Common.hs
--- a/src/Fcf/Data/Common.hs
+++ b/src/Fcf/Data/Common.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators #-}
 
 -- | Common data types: tuples, 'Either', 'Maybe'.
diff --git a/src/Fcf/Data/Function.hs b/src/Fcf/Data/Function.hs
--- a/src/Fcf/Data/Function.hs
+++ b/src/Fcf/Data/Function.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -28,9 +27,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval ('( 'True, 'Nothing) & Fst)
--- Eval ('( 'True, 'Nothing) & Fst) :: Bool
--- = 'True
+-- >>> :kind! Eval ('(True, Nothing) & Fst)
+-- Eval ('(True, Nothing) & Fst) :: Bool
+-- = True
 data (&) :: a -> (a -> Exp b) -> Exp b
 type instance Eval (x & f) = Eval (f x)
 
@@ -38,9 +37,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (((&&) `On` Fst) '( 'True, 'Nothing) '( 'False, 'Just '()))
--- Eval (((&&) `On` Fst) '( 'True, 'Nothing) '( 'False, 'Just '())) :: Bool
--- = 'False
+-- >>> :kind! Eval (((&&) `On` Fst) '(True, Nothing) '(False, Just '()))
+-- Eval (((&&) `On` Fst) '(True, Nothing) '(False, Just '())) :: Bool
+-- = False
 data On :: (b -> b -> Exp c) -> (a -> Exp b) -> a -> a -> Exp c
 type instance Eval (On r f x y) = Eval (r (Eval (f x)) (Eval (f y)))
 
@@ -48,8 +47,8 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Bicomap Fst Pure (||) '( 'False, 'Nothing) 'True)
--- Eval (Bicomap Fst Pure (||) '( 'False, 'Nothing) 'True) :: Bool
--- = 'True
+-- >>> :kind! Eval (Bicomap Fst Pure (||) '(False, Nothing) True)
+-- Eval (Bicomap Fst Pure (||) '(False, Nothing) True) :: Bool
+-- = True
 data Bicomap :: (a -> Exp c) -> (b -> Exp d) -> (c -> d -> Exp e) -> a -> b -> Exp e
 type instance Eval (Bicomap f g r x y) = Eval (r (Eval (f x)) (Eval (g y)))
diff --git a/src/Fcf/Data/List.hs b/src/Fcf/Data/List.hs
--- a/src/Fcf/Data/List.hs
+++ b/src/Fcf/Data/List.hs
@@ -2,7 +2,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
@@ -82,20 +81,26 @@
 import Fcf.Utils (If, TyEq)
 
 -- $setup
--- >>> import Fcf.Core (Eval)
+-- >>> :set -XGADTs -XUndecidableInstances
+-- >>> import Fcf.Core (Exp, Eval)
 -- >>> import Fcf.Combinators
+-- >>> import Fcf.Class.Foldable (Concat)
 -- >>> import Fcf.Class.Monoid ()
+-- >>> import Fcf.Data.Nat
+-- >>> import Fcf.Utils (If, TyEq)
+-- >>> import Data.Type.Ord ()
 -- >>> import qualified GHC.TypeLits as TL
 -- >>> import GHC.TypeLits (Nat)
-
+-- >>> import Numeric.Natural (Natural)
 
 -- | List catenation.
 --
 -- === __Example__
 --
--- >>> :kind! Eval ('[1, 2] ++ '[3, 4])
--- Eval ('[1, 2] ++ '[3, 4]) :: [Nat]
--- = '[1, 2, 3, 4]
+-- >>> data Example where Ex :: a -> Example  -- Hide the type of examples to avoid brittleness in different GHC versions
+-- >>> :kind! Ex (Eval ([1, 2] ++ [3, 4]) :: [Natural])
+-- Ex (Eval ([1, 2] ++ [3, 4]) :: [Natural]) :: Example
+-- = Ex [1, 2, 3, 4]
 --
 data (++) :: [a] -> [a] -> Exp [a]
 type instance Eval ((++) xs ys) = xs <> ys
@@ -133,12 +138,12 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Cons 1 '[2, 3])
--- Eval (Cons 1 '[2, 3]) :: [Nat]
--- = '[1, 2, 3]
--- >>> :kind! Eval (Cons Int '[Char, Maybe Double])
--- Eval (Cons Int '[Char, Maybe Double]) :: [*]
--- = '[Int, Char, Maybe Double]
+-- >>> :kind! Eval (Cons 1 [2, 3])
+-- Eval (Cons 1 [2, 3]) :: [Natural]
+-- = [1, 2, 3]
+-- >>> :kind! Eval (Cons Int [Char, Maybe Double])
+-- Eval (Cons Int [Char, Maybe Double]) :: [*]
+-- = [Int, Char, Maybe Double]
 --
 data Cons :: a -> [a] -> Exp [a]
 type instance Eval (Cons a as) = a ': as
@@ -151,9 +156,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Snoc '[1,2,3] 4)
--- Eval (Snoc '[1,2,3] 4) :: [Nat]
--- = '[1, 2, 3, 4]
+-- >>> :kind! Eval (Snoc [1,2,3] 4)
+-- Eval (Snoc [1,2,3] 4) :: [Natural]
+-- = [1, 2, 3, 4]
 data Snoc :: [a] -> a -> Exp [a]
 type instance Eval (Snoc lst a) = Eval (lst ++ '[a])
 
@@ -168,9 +173,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Reverse '[1,2,3,4,5])
--- Eval (Reverse '[1,2,3,4,5]) :: [Nat]
--- = '[5, 4, 3, 2, 1]
+-- >>> :kind! Eval (Reverse [1,2,3,4,5])
+-- Eval (Reverse [1,2,3,4,5]) :: [Natural]
+-- = [5, 4, 3, 2, 1]
 data Reverse :: [a] -> Exp [a]
 type instance Eval (Reverse l) = Eval (Rev l '[])
 
@@ -178,9 +183,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Intersperse 0 '[1,2,3,4])
--- Eval (Intersperse 0 '[1,2,3,4]) :: [Nat]
--- = '[1, 0, 2, 0, 3, 0, 4]
+-- >>> :kind! Eval (Intersperse 0 [1,2,3,4])
+-- Eval (Intersperse 0 [1,2,3,4]) :: [Natural]
+-- = [1, 0, 2, 0, 3, 0, 4]
 data Intersperse :: a -> [a] -> Exp [a]
 type instance Eval (Intersperse _   '[]      ) = '[]
 type instance Eval (Intersperse sep (x ': xs)) = x ': Eval (PrependToAll sep xs)
@@ -194,9 +199,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Intercalate '[", "] '[ '["Lorem"], '["ipsum"], '["dolor"] ])
--- Eval (Intercalate '[", "] '[ '["Lorem"], '["ipsum"], '["dolor"] ]) :: [TL.Symbol]
--- = '["Lorem", ", ", "ipsum", ", ", "dolor"]
+-- >>> :kind! Eval (Intercalate '[", "] [ '["Lorem"], '["ipsum"], '["dolor"] ])
+-- Eval (Intercalate '[", "] [ '["Lorem"], '["ipsum"], '["dolor"] ]) :: [TL.Symbol]
+-- = ["Lorem", ", ", "ipsum", ", ", "dolor"]
 data Intercalate :: [a] -> [[a]] -> Exp [a]
 type instance Eval (Intercalate xs xss) = Eval (Concat =<< Intersperse xs xss)
 
@@ -219,14 +224,14 @@
 -- >>> data ToThree :: Nat -> Exp (Maybe (Nat, Nat))
 -- >>> :{
 -- type instance Eval (ToThree b) =
---   If (Eval (b Fcf.>= 4))
---     'Nothing
---     ('Just '(b, b TL.+ 1))
+--   If (4 TL.<=? b)
+--     Nothing
+--     (Just '(b, b TL.+ 1))
 -- :}
 --
 -- >>> :kind! Eval (Unfoldr ToThree 0)
--- Eval (Unfoldr ToThree 0) :: [Nat]
--- = '[0, 1, 2, 3]
+-- Eval (Unfoldr ToThree 0) :: [Natural]
+-- = [0, 1, 2, 3]
 --
 -- See also the definition of `Replicate`.
 data Unfoldr :: (b -> Exp (Maybe (a, b))) -> b -> Exp [a]
@@ -245,8 +250,8 @@
 -- === __Example__
 --
 -- >>> :kind! Eval (Replicate 4 '("ok", 2))
--- Eval (Replicate 4 '("ok", 2)) :: [(TL.Symbol, Nat)]
--- = '[ '("ok", 2), '("ok", 2), '("ok", 2), '("ok", 2)]
+-- Eval (Replicate 4 '("ok", 2)) :: [(TL.Symbol, Natural)]
+-- = ['("ok", 2), '("ok", 2), '("ok", 2), '("ok", 2)]
 data Replicate :: Nat -> a -> Exp [a]
 type instance Eval (Replicate n a) = Eval (Unfoldr (NumIter a) n)
 
@@ -255,9 +260,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Take 2 '[1,2,3,4,5])
--- Eval (Take 2 '[1,2,3,4,5]) :: [Nat]
--- = '[1, 2]
+-- >>> :kind! Eval (Take 2 [1,2,3,4,5])
+-- Eval (Take 2 [1,2,3,4,5]) :: [Natural]
+-- = [1, 2]
 data Take :: Nat -> [a] -> Exp [a]
 type instance Eval (Take n as) = Take_ n as
 
@@ -270,9 +275,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Drop 2 '[1,2,3,4,5])
--- Eval (Drop 2 '[1,2,3,4,5]) :: [Nat]
--- = '[3, 4, 5]
+-- >>> :kind! Eval (Drop 2 [1,2,3,4,5])
+-- Eval (Drop 2 [1,2,3,4,5]) :: [Natural]
+-- = [3, 4, 5]
 data Drop :: Nat -> [a] -> Exp [a]
 type instance Eval (Drop n as) = Drop_ n as
 
@@ -285,9 +290,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (TakeWhile ((>=) 3) '[1, 2, 3, 4, 5])
--- Eval (TakeWhile ((>=) 3) '[1, 2, 3, 4, 5]) :: [Nat]
--- = '[1, 2, 3]
+-- >>> :kind! Eval (TakeWhile ((>=) 3) [1, 2, 3, 4, 5])
+-- Eval (TakeWhile ((>=) 3) [1, 2, 3, 4, 5]) :: [Natural]
+-- = [1, 2, 3]
 data TakeWhile :: (a -> Exp Bool) -> [a] -> Exp [a]
 type instance Eval (TakeWhile p '[]) = '[]
 type instance Eval (TakeWhile p (x ': xs)) =
@@ -300,9 +305,9 @@
 --
 -- === __Example__
 --
--- :kind! Eval (DropWhile ((>=) 3) '[1, 2, 3, 4, 5])
--- Eval (DropWhile ((>=) 3) '[1, 2, 3, 4, 5]) :: [Nat]
--- = '[4, 5]
+-- :kind! Eval (DropWhile ((>=) 3) [1, 2, 3, 4, 5])
+-- Eval (DropWhile ((>=) 3) [1, 2, 3, 4, 5]) :: [Natural]
+-- = [4, 5]
 data DropWhile :: (a -> Exp Bool) -> [a] -> Exp [a]
 type instance Eval (DropWhile p '[]) = '[]
 type instance Eval (DropWhile p (x ': xs)) =
@@ -320,17 +325,17 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Span (Flip (<) 3) '[1,2,3,4,1,2,3,4])
--- Eval (Span (Flip (<) 3) '[1,2,3,4,1,2,3,4]) :: ([Nat], [Nat])
--- = '( '[1, 2], '[3, 4, 1, 2, 3, 4])
+-- >>> :kind! Eval (Span (Flip (<) 3) [1,2,3,4,1,2])
+-- Eval (Span (Flip (<) 3) [1,2,3,4,1,2]) :: ([Natural], [Natural])
+-- = '([1, 2], [3, 4, 1, 2])
 --
--- >>> :kind! Eval (Span (Flip (<) 9) '[1,2,3])
--- Eval (Span (Flip (<) 9) '[1,2,3]) :: ([Nat], [Nat])
--- = '( '[1, 2, 3], '[])
+-- >>> :kind! Eval (Span (Flip (<) 9) [1,2,3])
+-- Eval (Span (Flip (<) 9) [1,2,3]) :: ([Natural], [Natural])
+-- = '([1, 2, 3], '[])
 --
--- >>> :kind! Eval (Span (Flip (<) 0) '[1,2,3])
--- Eval (Span (Flip (<) 0) '[1,2,3]) :: ([Nat], [Nat])
--- = '( '[], '[1, 2, 3])
+-- >>> :kind! Eval (Span (Flip (<) 0) [1,2,3])
+-- Eval (Span (Flip (<) 0) [1,2,3]) :: ([Natural], [Natural])
+-- = '( '[], [1, 2, 3])
 data Span :: (a -> Exp Bool) -> [a] -> Exp ([a],[a])
 type instance Eval (Span p lst) = '( Eval (TakeWhile p lst), Eval (DropWhile p lst))
 
@@ -341,17 +346,17 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Break (Flip (>) 3) '[1,2,3,4,1,2,3,4])
--- Eval (Break (Flip (>) 3) '[1,2,3,4,1,2,3,4]) :: ([Nat], [Nat])
--- = '( '[1, 2, 3], '[4, 1, 2, 3, 4])
+-- >>> :kind! Eval (Break (Flip (>) 3) [1,2,3,4,1,2])
+-- Eval (Break (Flip (>) 3) [1,2,3,4,1,2]) :: ([Natural], [Natural])
+-- = '([1, 2, 3], [4, 1, 2])
 --
--- >>> :kind! Eval (Break (Flip (<) 9) '[1,2,3])
--- Eval (Break (Flip (<) 9) '[1,2,3]) :: ([Nat], [Nat])
--- = '( '[], '[1, 2, 3])
+-- >>> :kind! Eval (Break (Flip (<) 9) [1,2,3])
+-- Eval (Break (Flip (<) 9) [1,2,3]) :: ([Natural], [Natural])
+-- = '( '[], [1, 2, 3])
 --
--- >>> :kind! Eval (Break (Flip (>) 9) '[1,2,3])
--- Eval (Break (Flip (>) 9) '[1,2,3]) :: ([Nat], [Nat])
--- = '( '[1, 2, 3], '[])
+-- >>> :kind! Eval (Break (Flip (>) 9) [1,2,3])
+-- Eval (Break (Flip (>) 9) [1,2,3]) :: ([Natural], [Natural])
+-- = '([1, 2, 3], '[])
 data Break :: (a -> Exp Bool) -> [a] -> Exp ([a],[a])
 type instance Eval (Break p lst) = Eval (Span (Not <=< p) lst)
 
@@ -360,9 +365,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Tails '[0,1,2,3])
--- Eval (Tails '[0,1,2,3]) :: [[Nat]]
--- = '[ '[0, 1, 2, 3], '[1, 2, 3], '[2, 3], '[3]]
+-- >>> :kind! Eval (Tails [0,1,2,3])
+-- Eval (Tails [0,1,2,3]) :: [[Natural]]
+-- = [[0, 1, 2, 3], [1, 2, 3], [2, 3], '[3]]
 data Tails :: [a] -> Exp [[a]]
 type instance Eval (Tails '[]) = '[]
 type instance Eval (Tails (a ': as)) = (a ': as) ': Eval (Tails as)
@@ -372,21 +377,21 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (IsPrefixOf '[0,1,2] '[0,1,2,3,4,5])
--- Eval (IsPrefixOf '[0,1,2] '[0,1,2,3,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval ([0,1,2] `IsPrefixOf` [0,1,2,3,4,5])
+-- Eval ([0,1,2] `IsPrefixOf` [0,1,2,3,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (IsPrefixOf '[0,1,2] '[0,1,3,2,4,5])
--- Eval (IsPrefixOf '[0,1,2] '[0,1,3,2,4,5]) :: Bool
--- = 'False
+-- >>> :kind! Eval ([0,1,2] `IsPrefixOf` [0,1,3,2,4,5])
+-- Eval ([0,1,2] `IsPrefixOf` [0,1,3,2,4,5]) :: Bool
+-- = False
 --
--- >>> :kind! Eval (IsPrefixOf '[] '[0,1,3,2,4,5])
--- Eval (IsPrefixOf '[] '[0,1,3,2,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval ('[] `IsPrefixOf` [0,1,3,2,4,5])
+-- Eval ('[] `IsPrefixOf` [0,1,3,2,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (IsPrefixOf '[0,1,3,2,4,5] '[])
--- Eval (IsPrefixOf '[0,1,3,2,4,5] '[]) :: Bool
--- = 'False
+-- >>> :kind! Eval ([0,1,3,2,4,5] `IsPrefixOf` '[])
+-- Eval ([0,1,3,2,4,5] `IsPrefixOf` '[]) :: Bool
+-- = False
 data IsPrefixOf :: [a] -> [a] -> Exp Bool
 type instance Eval (IsPrefixOf xs ys) = IsPrefixOf_ xs ys
 
@@ -402,21 +407,21 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (IsSuffixOf '[3,4,5] '[0,1,2,3,4,5])
--- Eval (IsSuffixOf '[3,4,5] '[0,1,2,3,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval (IsSuffixOf [3,4,5] [0,1,2,3,4,5])
+-- Eval (IsSuffixOf [3,4,5] [0,1,2,3,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (IsSuffixOf '[3,4,5] '[0,1,3,2,4,5])
--- Eval (IsSuffixOf '[3,4,5] '[0,1,3,2,4,5]) :: Bool
--- = 'False
+-- >>> :kind! Eval (IsSuffixOf [3,4,5] [0,1,3,2,4,5])
+-- Eval (IsSuffixOf [3,4,5] [0,1,3,2,4,5]) :: Bool
+-- = False
 --
--- >>> :kind! Eval (IsSuffixOf '[] '[0,1,3,2,4,5])
--- Eval (IsSuffixOf '[] '[0,1,3,2,4,5]) :: Bool
--- = 'True
+-- >>> :kind! Eval (IsSuffixOf '[] [0,1,3,2,4,5])
+-- Eval (IsSuffixOf '[] [0,1,3,2,4,5]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (IsSuffixOf '[0,1,3,2,4,5] '[])
--- Eval (IsSuffixOf '[0,1,3,2,4,5] '[]) :: Bool
--- = 'False
+-- >>> :kind! Eval (IsSuffixOf [0,1,3,2,4,5] '[])
+-- Eval (IsSuffixOf [0,1,3,2,4,5] '[]) :: Bool
+-- = False
 data IsSuffixOf :: [a] -> [a] -> Exp Bool
 type instance Eval (IsSuffixOf xs ys) =
   Eval (IsPrefixOf (Reverse @@ xs) (Reverse @@ ys))
@@ -426,13 +431,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (IsInfixOf '[2,3,4] '[0,1,2,3,4,5,6])
--- Eval (IsInfixOf '[2,3,4] '[0,1,2,3,4,5,6]) :: Bool
--- = 'True
+-- >>> :kind! Eval (IsInfixOf [2,3,4] [0,1,2,3,4,5,6])
+-- Eval (IsInfixOf [2,3,4] [0,1,2,3,4,5,6]) :: Bool
+-- = True
 --
--- >>> :kind! Eval (IsInfixOf '[2,4,4] '[0,1,2,3,4,5,6])
--- Eval (IsInfixOf '[2,4,4] '[0,1,2,3,4,5,6]) :: Bool
--- = 'False
+-- >>> :kind! Eval (IsInfixOf [2,4,4] [0,1,2,3,4,5,6])
+-- Eval (IsInfixOf [2,4,4] [0,1,2,3,4,5,6]) :: Bool
+-- = False
 data IsInfixOf :: [a] -> [a] -> Exp Bool
 type instance Eval (IsInfixOf xs ys) = Eval (Any (IsPrefixOf xs) =<< Tails ys)
 
@@ -443,12 +448,12 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Elem 1 '[1,2,3])
--- Eval (Elem 1 '[1,2,3]) :: Bool
--- = 'True
--- >>> :kind! Eval (Elem 1 '[2,3])
--- Eval (Elem 1 '[2,3]) :: Bool
--- = 'False
+-- >>> :kind! Eval (Elem 1 [1,2,3])
+-- Eval (Elem 1 [1,2,3]) :: Bool
+-- = True
+-- >>> :kind! Eval (Elem 1 [2,3])
+-- Eval (Elem 1 [2,3]) :: Bool
+-- = False
 --
 data Elem :: a -> [a] -> Exp Bool
 type instance Eval (Elem a as) = Eval (IsJust =<< FindIndex (TyEq a) as)
@@ -464,13 +469,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Find (TyEq 0) '[1,2,3])
--- Eval (Find (TyEq 0) '[1,2,3]) :: Maybe Nat
--- = 'Nothing
+-- >>> :kind! Eval (Find (TyEq 0) [1,2,3])
+-- Eval (Find (TyEq 0) [1,2,3]) :: Maybe Natural
+-- = Nothing
 --
--- >>> :kind! Eval (Find (TyEq 0) '[1,2,3,0])
--- Eval (Find (TyEq 0) '[1,2,3,0]) :: Maybe Nat
--- = 'Just 0
+-- >>> :kind! Eval (Find (TyEq 0) [1,2,3,0])
+-- Eval (Find (TyEq 0) [1,2,3,0]) :: Maybe Natural
+-- = Just 0
 data Find :: (a -> Exp Bool) -> [a] -> Exp (Maybe a)
 type instance Eval (Find _p '[]) = 'Nothing
 type instance Eval (Find p (a ': as)) =
@@ -483,9 +488,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Filter ((>) 3) '[1,2,3,0])
--- Eval (Filter ((>) 3) '[1,2,3,0]) :: [Nat]
--- = '[1, 2, 0]
+-- >>> :kind! Eval (Filter ((>) 3) [1,2,3,0])
+-- Eval (Filter ((>) 3) [1,2,3,0]) :: [Natural]
+-- = [1, 2, 0]
 data Filter :: (a -> Exp Bool) -> [a] -> Exp [a]
 type instance Eval (Filter _p '[]) = '[]
 type instance Eval (Filter p (a ': as)) =
@@ -499,9 +504,10 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (Partition ((>=) 35) '[ 20, 30, 40, 50])
--- Eval (Partition ((>=) 35) '[ 20, 30, 40, 50]) :: ([Nat], [Nat])
--- = '( '[20, 30], '[40, 50])
+-- >>> :kind! Eval (Partition ((>=) 35) [20, 30, 40, 50])
+-- Eval (Partition ((>=) 35) [20, 30, 40, 50]) :: ([Natural],
+--                                                 [Natural])
+-- = '([20, 30], [40, 50])
 data Partition :: (a -> Exp Bool) -> [a] -> Exp ([a], [a])
 type instance Eval (Partition p lst) = Eval (Foldr (PartHelp p) '( '[], '[]) lst)
 
@@ -517,13 +523,13 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (FindIndex ((<=) 3) '[1,2,3,1,2,3])
--- Eval (FindIndex ((<=) 3) '[1,2,3,1,2,3]) :: Maybe Nat
--- = 'Just 2
+-- >>> :kind! Eval (FindIndex ((<=) 3) [1,2,3,1,2,3])
+-- Eval (FindIndex ((<=) 3) [1,2,3,1,2,3]) :: Maybe Natural
+-- = Just 2
 --
--- >>> :kind! Eval (FindIndex ((>) 0) '[1,2,3,1,2,3])
--- Eval (FindIndex ((>) 0) '[1,2,3,1,2,3]) :: Maybe Nat
--- = 'Nothing
+-- >>> :kind! Eval (FindIndex ((>) 0) [1,2,3,1,2,3])
+-- Eval (FindIndex ((>) 0) [1,2,3,1,2,3]) :: Maybe Natural
+-- = Nothing
 data FindIndex :: (a -> Exp Bool) -> [a] -> Exp (Maybe Nat)
 type instance Eval (FindIndex _p '[]) = 'Nothing
 type instance Eval (FindIndex p (a ': as)) =
@@ -538,9 +544,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (SetIndex 2 7 '[1,2,3])
--- Eval (SetIndex 2 7 '[1,2,3]) :: [Nat]
--- = '[1, 2, 7]
+-- >>> :kind! Eval (SetIndex 2 7 [1,2,3])
+-- Eval (SetIndex 2 7 [1,2,3]) :: [Natural]
+-- = [1, 2, 7]
 data SetIndex :: Nat -> a -> [a] -> Exp [a]
 type instance Eval (SetIndex n a' as) = SetIndexImpl n a' as
 
@@ -553,9 +559,9 @@
 --
 -- === __Example__
 --
--- >>> :kind! Eval (ZipWith (+) '[1,2,3] '[1,1,1])
--- Eval (ZipWith (+) '[1,2,3] '[1,1,1]) :: [Nat]
--- = '[2, 3, 4]
+-- >>> :kind! Eval (ZipWith (+) [1,2,3] [1,1,1])
+-- Eval (ZipWith (+) [1,2,3] [1,1,1]) :: [Natural]
+-- = [2, 3, 4]
 data ZipWith :: (a -> b -> Exp c) -> [a] -> [b] -> Exp [c]
 type instance Eval (ZipWith _f '[] _bs) = '[]
 type instance Eval (ZipWith _f _as '[]) = '[]
diff --git a/src/Fcf/Data/Nat.hs b/src/Fcf/Data/Nat.hs
--- a/src/Fcf/Data/Nat.hs
+++ b/src/Fcf/Data/Nat.hs
@@ -3,7 +3,6 @@
     DataKinds,
     PolyKinds,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}
 
diff --git a/src/Fcf/Data/Symbol.hs b/src/Fcf/Data/Symbol.hs
--- a/src/Fcf/Data/Symbol.hs
+++ b/src/Fcf/Data/Symbol.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE DataKinds              #-}
 {-# LANGUAGE PolyKinds              #-}
 {-# LANGUAGE TypeFamilies           #-}
-{-# LANGUAGE TypeInType             #-}
 {-# LANGUAGE TypeOperators          #-}
 {-# LANGUAGE UndecidableInstances   #-}
 {-# OPTIONS_GHC -Wall                       #-}
diff --git a/src/Fcf/Utils.hs b/src/Fcf/Utils.hs
--- a/src/Fcf/Utils.hs
+++ b/src/Fcf/Utils.hs
@@ -5,7 +5,6 @@
     PolyKinds,
     RankNTypes,
     TypeFamilies,
-    TypeInType,
     TypeOperators,
     UndecidableInstances #-}