From d0f887c9045960b59ae40bb7d77f3f55cbb9ed02 Mon Sep 17 00:00:00 2001
From: Mikolaj Konarski <mikolaj.konarski@funktory.com>
Date: Tue, 13 Jan 2026 12:11:18 +0100
Subject: Let X.fromListOuterSN and ravelOuterN take NonEmpty

---
 src/Data/Array/Nested/Mixed.hs |  3 +--
 src/Data/Array/XArray.hs       | 13 ++++++-------
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/Data/Array/Nested/Mixed.hs b/src/Data/Array/Nested/Mixed.hs
index b0d32db..f0dadb4 100644
--- a/src/Data/Array/Nested/Mixed.hs
+++ b/src/Data/Array/Nested/Mixed.hs
@@ -28,7 +28,6 @@ import Control.Monad.ST
 import Data.Array.RankedS qualified as S
 import Data.Bifunctor (bimap)
 import Data.Coerce
-import Data.Foldable (toList)
 import Data.Int
 import Data.Kind (Type)
 import Data.List.NonEmpty (NonEmpty(..))
@@ -423,7 +422,7 @@ instance Storable a => Elt (Primitive a) where
   mscalar (Primitive x) = M_Primitive ZSX (X.scalar x)
   mfromListOuterSN sn l@(arr1 :| _) =
     let sh = mshape arr1
-    in M_Primitive (SKnown sn :$% sh) (X.fromListOuterSN sn sh (map (\(M_Primitive _ a) -> a) (toList l)))
+    in M_Primitive (SKnown sn :$% sh) (X.fromListOuterSN sn sh ((\(M_Primitive _ a) -> a) <$> l))
   mtoListOuter (M_Primitive sh arr) = map (M_Primitive (shxTail sh)) (X.toListOuter arr)
 
   {-# INLINE mlift #-}
diff --git a/src/Data/Array/XArray.hs b/src/Data/Array/XArray.hs
index 77c0dc0..f779a53 100644
--- a/src/Data/Array/XArray.hs
+++ b/src/Data/Array/XArray.hs
@@ -26,7 +26,7 @@ import Data.Array.RankedS qualified as S
 import Data.Coerce
 import Data.Foldable (toList)
 import Data.Kind
-import Data.List.NonEmpty (NonEmpty)
+import Data.List.NonEmpty (NonEmpty(..))
 import Data.Proxy
 import Data.Type.Equality
 import Data.Type.Ord
@@ -312,22 +312,21 @@ sumOuter ssh ssh' arr
 -- in the given shape to guess the shape of the empty array, in general).
 {-# INLINE fromListOuterSN #-}
 fromListOuterSN :: forall n sh a. Storable a
-                => SNat n -> IShX sh -> [XArray sh a] -> XArray (Just n : sh) a
+                => SNat n -> IShX sh -> NonEmpty (XArray sh a) -> XArray (Just n : sh) a
 fromListOuterSN m sh l
   | Dict <- lemKnownNatRank sh
-  , let l' = coerce @[XArray sh a] @[S.Array (Rank sh) a] l
+  , let l' = coerce @(NonEmpty (XArray sh a)) @(NonEmpty (S.Array (Rank sh) a)) l
   = case sh of
-      ZSX -> fromList1SN m (map S.unScalar l')
+      ZSX -> fromList1SN m (map S.unScalar (toList l'))
       _ -> XArray (ravelOuterN (fromSNat' m) l')
 
 -- | This checks that the list has the given length and that all shapes in the
 -- list are equal. The list must be non-empty, and is streamed.
 {-# INLINEABLE ravelOuterN #-}
 ravelOuterN :: (KnownNat k, Storable a)
-            => Int -> [S.Array k a] -> S.Array (1 + k) a
+            => Int -> NonEmpty (S.Array k a) -> S.Array (1 + k) a
 ravelOuterN 0 _ = error "ravelOuterN: N == 0"
-ravelOuterN _ [] = error "ravelOuterN: empty list"
-ravelOuterN k as@(a0 : _) = runST $ do
+ravelOuterN k as@(a0 :| _) = runST $ do
   let sh0 = S.shapeL a0
       len = product sh0
       vecSize = k * len
-- 
cgit v1.2.3-70-g09d2