1 files changed, 18 insertions, 7 deletions
diff --git a/src/Data/Array/Nested/Internal/Mixed.hs b/src/Data/Array/Nested/Internal/Mixed.hs
index 215313e..50202ba 100644
--- a/src/Data/Array/Nested/Internal/Mixed.hs
+++ b/src/Data/Array/Nested/Internal/Mixed.hs
@@ -104,7 +104,7 @@ newtype Primitive a = Primitive a
 
 -- | Element types that are primitive; arrays of these types are just a newtype
 -- wrapper over an array.
-class Storable a => PrimElt a where
+class (Storable a, Elt a) => PrimElt a where
   fromPrimitive :: Mixed sh (Primitive a) -> Mixed sh a
   toPrimitive :: Mixed sh a -> Mixed sh (Primitive a)
 
@@ -854,15 +854,26 @@ mmaxIndexPrim :: (PrimElt a, NumElt a) => Mixed sh a -> IIxX sh
 mmaxIndexPrim (toPrimitive -> M_Primitive sh (XArray arr)) =
   ixxFromList (ssxFromShape sh) (numEltMaxIndex arr)
 
-mdot1 :: (PrimElt a, NumElt a) => Mixed '[n] a -> Mixed '[n] a -> a
-mdot1 (toPrimitive -> M_Primitive _ (XArray arr1)) (toPrimitive -> M_Primitive _ (XArray arr2)) =
-  numEltDotprod arr1 arr2
+mdot1Inner :: forall sh n a. (PrimElt a, NumElt a)
+           => Proxy n -> Mixed (sh ++ '[n]) a -> Mixed (sh ++ '[n]) a -> Mixed sh a
+mdot1Inner _ (toPrimitive -> M_Primitive sh1 (XArray a)) (toPrimitive -> M_Primitive sh2 (XArray b))
+  | Refl <- lemInitApp (Proxy @sh) (Proxy @n)
+  , Refl <- lemLastApp (Proxy @sh) (Proxy @n)
+  = case sh1 of
+      _ :$% _
+        | sh1 == sh2
+        , Refl <- lemRankApp (ssxInit (ssxFromShape sh1)) (ssxLast (ssxFromShape sh1) :!% ZKX) ->
+            fromPrimitive $ M_Primitive (shxInit sh1) (XArray (numEltDotprodInner (shxRank (shxInit sh1)) a b))
+        | otherwise -> error "mdot1Inner: Unequal shapes"
+      ZSX -> error "unreachable"
 
 -- | This has a temporary, suboptimal implementation in terms of 'mflatten'.
--- Prefer 'mdot1' if applicable.
+-- Prefer 'mdot1Inner' if applicable.
 mdot :: (PrimElt a, NumElt a) => Mixed sh a -> Mixed sh a -> a
-mdot a b = mdot1 (fromPrimitive (mflatten (toPrimitive a)))
-                 (fromPrimitive (mflatten (toPrimitive b)))
+mdot a b =
+  munScalar $
+    mdot1Inner Proxy (fromPrimitive (mflatten (toPrimitive a)))
+                     (fromPrimitive (mflatten (toPrimitive b)))
 
 mtoXArrayPrimP :: Mixed sh (Primitive a) -> (IShX sh, XArray sh a)
 mtoXArrayPrimP (M_Primitive sh arr) = (sh, arr)