From 24a21e3807453312ee92ed68f977cd9523d49491 Mon Sep 17 00:00:00 2001
From: George Thomas <georgefsthomas@gmail.com>
Date: Mon, 5 Jan 2026 15:19:18 +0000
Subject: [PATCH] Remove heterogenous list length function

---
 haskell/Main.hs |  2 +-
 haskell/Pre.hs  | 10 ----------
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/haskell/Main.hs b/haskell/Main.hs
index 10b9142..136f0c2 100644
--- a/haskell/Main.hs
+++ b/haskell/Main.hs
@@ -47,7 +47,7 @@ main =
                                     mapHListF (\(Fanout (f, Op o)) -> (o &&& id) $ f input) parts
                          in pure (input, rs, os)
                     )
-                    $ ( flip map ([0 :: Int .. hlistfLength parts - 1]) $
+                    $ ( flip map ([0 :: Int .. foldHListF0 (const succ) 0 parts - 1]) $
                             \n@(show . succ -> nt) ->
                                 TestTree
                                     (mkTestName nt)
diff --git a/haskell/Pre.hs b/haskell/Pre.hs
index 60935c6..5ad7086 100644
--- a/haskell/Pre.hs
+++ b/haskell/Pre.hs
@@ -40,12 +40,10 @@ module Pre (
     adjacentPairs,
     sortPair,
     HList (..),
-    hlistLength,
     HListF (..),
     foldHListF,
     foldHListF0,
     mapHListF,
-    hlistfLength,
     (/\),
     (/\\),
     nil,
@@ -160,10 +158,6 @@ data HList (as :: List Type) :: Type where
         a ->
         HList as ->
         HList (a ': as)
-hlistLength :: HList r -> Int
-hlistLength = \case
-    HNil -> 0
-    HCons _ l -> 1 + hlistLength l
 
 data HListF (f :: Type -> Type) (as :: List Type) :: Type where
     HNilF :: HListF f '[]
@@ -181,10 +175,6 @@ foldHListF0 f e = \case
     HConsF x xs -> f x $ foldHListF0 f e xs
 mapHListF :: (forall a. f a -> g a) -> HListF f as -> HListF g as
 mapHListF t = foldHListF (\x r -> HConsF (t x) $ r) HNilF
-hlistfLength :: HListF f r -> Int
-hlistfLength = \case
-    HNilF -> 0
-    HConsF _ l -> 1 + hlistfLength l
 
 newtype Fanout f g a = Fanout (f a, g a)