3 files changed, 13 insertions, 2 deletions
diff --git a/src/Data/Array/Mixed/Shape.hs b/src/Data/Array/Mixed/Shape.hs
index 4ab3c26..4343574 100644
--- a/src/Data/Array/Mixed/Shape.hs
+++ b/src/Data/Array/Mixed/Shape.hs
@@ -252,6 +252,9 @@ instance NFData i => NFData (ShX sh i) where
 shxLength :: ShX sh i -> Int
 shxLength (ShX l) = listxLength l
 
+shxLengthSNat :: ShX sh f -> SNat (Rank sh)
+shxLengthSNat (ShX list) = listxLengthSNat list
+
 -- | This is more than @geq@: it also checks that the integers (the unknown
 -- dimensions) are the same.
 shxEqual :: Eq i => ShX sh i -> ShX sh' i -> Maybe (sh :~: sh')
diff --git a/src/Data/Array/Nested.hs b/src/Data/Array/Nested.hs
index 1c9cebc..370cfc8 100644
--- a/src/Data/Array/Nested.hs
+++ b/src/Data/Array/Nested.hs
@@ -6,7 +6,7 @@ module Data.Array.Nested (
   ListR(ZR, (:::)),
   IxR(.., ZIR, (:.:)), IIxR,
   ShR(.., ZSR, (:$:)), IShR,
-  rshape, rindex, rindexPartial, rgenerate, rsumOuter1,
+  rshape, rrank, rindex, rindexPartial, rgenerate, rsumOuter1,
   rtranspose, rappend, rscalar, rfromVector, rtoVector, runScalar,
   rrerank,
   rreplicate, rreplicateScal, rfromListOuter, rfromList1, rfromList1Prim, rtoListOuter, rtoList1,
@@ -16,7 +16,7 @@ module Data.Array.Nested (
   -- ** Conversions
   rtoXArrayPrim, rfromXArrayPrim,
   rcastToShaped,
-  rfromOrthotope,
+  rfromOrthotope, rtoOrthotope,
 
   -- * Shaped arrays
   Shaped(Shaped),
diff --git a/src/Data/Array/Nested/Internal/Ranked.hs b/src/Data/Array/Nested/Internal/Ranked.hs
index d6eff31..894ed0d 100644
--- a/src/Data/Array/Nested/Internal/Ranked.hs
+++ b/src/Data/Array/Nested/Internal/Ranked.hs
@@ -215,6 +215,9 @@ instance (FloatElt a, NumElt a, PrimElt a) => Floating (Ranked n a) where
 rshape :: forall n a. Elt a => Ranked n a -> IShR n
 rshape (Ranked arr) = shCvtXR' (mshape arr)
 
+rrank :: Elt a => Ranked n a -> SNat n
+rrank = shrToSNat . rshape
+
 rindex :: Elt a => Ranked n a -> IIxR n -> a
 rindex (Ranked arr) idx = mindex arr (ixCvtRX idx)
 
@@ -331,6 +334,11 @@ rfromOrthotope sn arr
   = let xarr = XArray arr
     in Ranked (fromPrimitive (M_Primitive (X.shape (ssxFromSNat sn) xarr) xarr))
 
+rtoOrthotope :: PrimElt a => Ranked n a -> S.Array n a
+rtoOrthotope (rtoPrimitive -> Ranked (M_Primitive sh (XArray arr)))
+  | Refl <- lemRankReplicate (shrToSNat $ shCvtXR' sh)
+  = arr
+
 runScalar :: Elt a => Ranked 0 a -> a
 runScalar arr = rindex arr ZIR