From 67b62499a6d60fed9489f0371a8c841beb0c308f Mon Sep 17 00:00:00 2001
From: Mikolaj Konarski <mikolaj.konarski@funktory.com>
Date: Sat, 4 Apr 2026 23:08:58 +0200
Subject: Use lazilyConcat for listxAppend

---
 src/Data/Array/Nested/Shaped/Shape.hs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'src/Data/Array/Nested/Shaped/Shape.hs')

diff --git a/src/Data/Array/Nested/Shaped/Shape.hs b/src/Data/Array/Nested/Shaped/Shape.hs
index 13596a7..fe55d1a 100644
--- a/src/Data/Array/Nested/Shaped/Shape.hs
+++ b/src/Data/Array/Nested/Shaped/Shape.hs
@@ -119,9 +119,9 @@ listsLast :: ListS (n : sh) i -> i
 listsLast (_ ::$ sh@(_ ::$ _)) = listsLast sh
 listsLast (n ::$ ZS) = n
 
-listsAppend :: ListS sh i -> ListS sh' i -> ListS (sh ++ sh') i
-listsAppend ZS idx' = idx'
-listsAppend (i ::$ idx) idx' = i ::$ listsAppend idx idx'
+listsAppend :: forall sh sh' i. ListS sh i -> ListS sh' i -> ListS (sh ++ sh') i
+listsAppend = gcastWith (unsafeCoerceRefl :: MapJust (sh ++ sh') :~: MapJust sh ++ MapJust sh') $
+              coerce (listxAppend @_ @_ @i)
 
 listsZip :: ListS sh i -> ListS sh j -> ListS sh (i, j)
 listsZip ZS ZS = ZS
@@ -219,7 +219,7 @@ ixsCast ZIS = ZIS
 ixsCast (i :.$ idx) = i :.$ ixsCast idx
 
 ixsAppend :: forall sh sh' i. IxS sh i -> IxS sh' i -> IxS (sh ++ sh') i
-ixsAppend = coerce (listsAppend @_ @i)
+ixsAppend = coerce (listsAppend @_ @_ @i)
 
 ixsZip :: IxS sh i -> IxS sh j -> IxS sh (i, j)
 ixsZip ZIS ZIS = ZIS
-- 
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