4 files changed, 24 insertions, 12 deletions
diff --git a/src/Data/Array/Nested.hs b/src/Data/Array/Nested.hs
index f987acc..b825691 100644
--- a/src/Data/Array/Nested.hs
+++ b/src/Data/Array/Nested.hs
@@ -8,6 +8,7 @@ module Data.Array.Nested (
   ShR(.., ZSR, (:$:)), IShR,
   rshape, rrank, rsize, rindex, rindexPartial, rgenerate, rsumOuter1, rsumAllPrim,
   rtranspose, rappend, rconcat, rscalar, rfromVector, rtoVector, runScalar,
+  remptyArray,
   rrerank,
   rreplicate, rreplicateScal, rfromListOuter, rfromList1, rfromList1Prim, rtoListOuter, rtoList1,
   rfromListLinear, rfromListPrimLinear, rtoListLinear,
@@ -29,6 +30,7 @@ module Data.Array.Nested (
   sshape, srank, ssize, sindex, sindexPartial, sgenerate, ssumOuter1, ssumAllPrim,
   stranspose, sappend, sscalar, sfromVector, stoVector, sunScalar,
   -- TODO: sconcat? What should its type be?
+  semptyArray,
   srerank,
   sreplicate, sreplicateScal, sfromListOuter, sfromList1, sfromList1Prim, stoListOuter, stoList1,
   sfromListLinear, sfromListPrimLinear, stoListLinear,
@@ -50,6 +52,7 @@ module Data.Array.Nested (
   SMayNat(..),
   mshape, mrank, msize, mindex, mindexPartial, mgenerate, msumOuter1, msumAllPrim,
   mtranspose, mappend, mconcat, mscalar, mfromVector, mtoVector, munScalar,
+  memptyArray,
   mrerank,
   mreplicate, mreplicateScal, mfromListOuter, mfromList1, mfromList1Prim, mtoListOuter, mtoList1,
   mfromListLinear, mfromListPrimLinear, mtoListLinear,
diff --git a/src/Data/Array/Nested/Internal/Mixed.hs b/src/Data/Array/Nested/Internal/Mixed.hs
index 0e4f5e6..8d239cf 100644
--- a/src/Data/Array/Nested/Internal/Mixed.hs
+++ b/src/Data/Array/Nested/Internal/Mixed.hs
@@ -366,7 +366,7 @@ class Elt a where
 -- 'Data.Array.Nested.Shaped.sgenerate'.
 class Elt a => KnownElt a where
   -- | Create an empty array. The given shape must have size zero; this may or may not be checked.
-  memptyArray :: IShX sh -> Mixed sh a
+  memptyArrayUnsafe :: IShX sh -> Mixed sh a
 
   -- | Create uninitialised vectors for this array type, given the shape of
   -- this vector and an example for the contents.
@@ -461,7 +461,7 @@ deriving via Primitive Float instance Elt Float
 deriving via Primitive () instance Elt ()
 
 instance Storable a => KnownElt (Primitive a) where
-  memptyArray sh = M_Primitive sh (X.empty sh)
+  memptyArrayUnsafe sh = M_Primitive sh (X.empty sh)
   mvecsUnsafeNew sh _ = MV_Primitive <$> VSM.unsafeNew (shxSize sh)
   mvecsNewEmpty _ = MV_Primitive <$> VSM.unsafeNew 0
 
@@ -517,7 +517,7 @@ instance (Elt a, Elt b) => Elt (a, b) where
   mvecsFreeze sh (MV_Tup2 a b) = M_Tup2 <$> mvecsFreeze sh a <*> mvecsFreeze sh b
 
 instance (KnownElt a, KnownElt b) => KnownElt (a, b) where
-  memptyArray sh = M_Tup2 (memptyArray sh) (memptyArray sh)
+  memptyArrayUnsafe sh = M_Tup2 (memptyArrayUnsafe sh) (memptyArrayUnsafe sh)
   mvecsUnsafeNew sh (x, y) = MV_Tup2 <$> mvecsUnsafeNew sh x <*> mvecsUnsafeNew sh y
   mvecsNewEmpty _ = MV_Tup2 <$> mvecsNewEmpty (Proxy @a) <*> mvecsNewEmpty (Proxy @b)
 
@@ -650,7 +650,7 @@ instance Elt a => Elt (Mixed sh' a) where
   mvecsFreeze sh (MV_Nest sh' vecs) = M_Nest sh <$> mvecsFreeze (shxAppend sh sh') vecs
 
 instance (KnownShX sh', KnownElt a) => KnownElt (Mixed sh' a) where
-  memptyArray sh = M_Nest sh (memptyArray (shxAppend sh (shxCompleteZeros (knownShX @sh'))))
+  memptyArrayUnsafe sh = M_Nest sh (memptyArrayUnsafe (shxAppend sh (shxCompleteZeros (knownShX @sh'))))
 
   mvecsUnsafeNew sh example
     | shxSize sh' == 0 = mvecsNewEmpty (Proxy @(Mixed sh' a))
@@ -661,6 +661,9 @@ instance (KnownShX sh', KnownElt a) => KnownElt (Mixed sh' a) where
   mvecsNewEmpty _ = MV_Nest (shxCompleteZeros (knownShX @sh')) <$> mvecsNewEmpty (Proxy @a)
 
 
+memptyArray :: KnownElt a => IShX sh -> Mixed (Just 0 : sh) a
+memptyArray sh = memptyArrayUnsafe (SKnown SNat :$% sh)
+
 mrank :: Elt a => Mixed sh a -> SNat (Rank sh)
 mrank = shxRank . mshape
 
@@ -687,12 +690,12 @@ msize = shxSize . mshape
 -- easily, hence the runtime check.
 mgenerate :: forall sh a. KnownElt a => IShX sh -> (IIxX sh -> a) -> Mixed sh a
 mgenerate sh f = case shxEnum sh of
-  [] -> memptyArray sh
+  [] -> memptyArrayUnsafe sh
   firstidx : restidxs ->
     let firstelem = f (ixxZero' sh)
         shapetree = mshapeTree firstelem
     in if mshapeTreeEmpty (Proxy @a) shapetree
-         then memptyArray sh
+         then memptyArrayUnsafe sh
          else runST $ do
                 vecs <- mvecsUnsafeNew sh firstelem
                 mvecsWrite sh firstidx firstelem vecs
diff --git a/src/Data/Array/Nested/Internal/Ranked.hs b/src/Data/Array/Nested/Internal/Ranked.hs
index 39a6018..9e8a7b2 100644
--- a/src/Data/Array/Nested/Internal/Ranked.hs
+++ b/src/Data/Array/Nested/Internal/Ranked.hs
@@ -165,11 +165,11 @@ instance Elt a => Elt (Ranked n a) where
                     vecs)
 
 instance (KnownNat n, KnownElt a) => KnownElt (Ranked n a) where
-  memptyArray :: forall sh. IShX sh -> Mixed sh (Ranked n a)
-  memptyArray i
+  memptyArrayUnsafe :: forall sh. IShX sh -> Mixed sh (Ranked n a)
+  memptyArrayUnsafe i
     | Dict <- lemKnownReplicate (SNat @n)
     = coerce @(Mixed sh (Mixed (Replicate n Nothing) a)) @(Mixed sh (Ranked n a)) $
-        memptyArray i
+        memptyArrayUnsafe i
 
   mvecsUnsafeNew idx (Ranked arr)
     | Dict <- lemKnownReplicate (SNat @n)
@@ -229,6 +229,9 @@ instance (FloatElt a, NumElt a, PrimElt a, Num a) => Floating (Ranked n a) where
   log1mexp = arithPromoteRanked GHC.Float.log1mexp
 
 
+remptyArray :: KnownElt a => Ranked 1 a
+remptyArray = mtoRanked (memptyArray ZSX)
+
 rshape :: Elt a => Ranked n a -> IShR n
 rshape (Ranked arr) = shCvtXR' (mshape arr)
 
diff --git a/src/Data/Array/Nested/Internal/Shaped.hs b/src/Data/Array/Nested/Internal/Shaped.hs
index e2f65c0..228d800 100644
--- a/src/Data/Array/Nested/Internal/Shaped.hs
+++ b/src/Data/Array/Nested/Internal/Shaped.hs
@@ -163,11 +163,11 @@ instance Elt a => Elt (Shaped sh a) where
                     vecs)
 
 instance (KnownShS sh, KnownElt a) => KnownElt (Shaped sh a) where
-  memptyArray :: forall sh'. IShX sh' -> Mixed sh' (Shaped sh a)
-  memptyArray i
+  memptyArrayUnsafe :: forall sh'. IShX sh' -> Mixed sh' (Shaped sh a)
+  memptyArrayUnsafe i
     | Dict <- lemKnownMapJust (Proxy @sh)
     = coerce @(Mixed sh' (Mixed (MapJust sh) a)) @(Mixed sh' (Shaped sh a)) $
-        memptyArray i
+        memptyArrayUnsafe i
 
   mvecsUnsafeNew idx (Shaped arr)
     | Dict <- lemKnownMapJust (Proxy @sh)
@@ -239,6 +239,9 @@ instance (FloatElt a, NumElt a, PrimElt a, Floating a, KnownShS sh) => Floating
   log1mexp = arithPromoteShaped GHC.Float.log1mexp
 
 
+semptyArray :: KnownElt a => ShS sh -> Shaped (0 : sh) a
+semptyArray sh = Shaped (memptyArray (shCvtSX sh))
+
 sshape :: forall sh a. Elt a => Shaped sh a -> ShS sh
 sshape (Shaped arr) = shCvtXS' (mshape arr)