2 files changed, 54 insertions, 6 deletions
diff --git a/src/Data/Array/Nested.hs b/src/Data/Array/Nested.hs
index 148acf5..f383b99 100644
--- a/src/Data/Array/Nested.hs
+++ b/src/Data/Array/Nested.hs
@@ -1,8 +1,9 @@
 {-# LANGUAGE ExplicitNamespaces #-}
+{-# LANGUAGE PatternSynonyms #-}
 module Data.Array.Nested (
   -- * Ranked arrays
   Ranked,
-  IxR(..), IIxR,
+  IxR, pattern (:.:), pattern ZIR, IIxR,
   rshape, rindex, rindexPartial, rgenerate, rsumOuter1,
   rtranspose, rappend, rscalar, rfromVector, runScalar,
   rconstant, rfromList, rfromList1, rtoList, rtoList1,
diff --git a/src/Data/Array/Nested/Internal.hs b/src/Data/Array/Nested/Internal.hs
index 0582a14..e42de12 100644
--- a/src/Data/Array/Nested/Internal.hs
+++ b/src/Data/Array/Nested/Internal.hs
@@ -15,6 +15,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE ViewPatterns #-}
 {-# OPTIONS_GHC -fplugin GHC.TypeLits.KnownNat.Solver #-}
 
 {-|
@@ -849,17 +850,63 @@ instance (KnownINat n, Storable a, Num a) => Num (Ranked n (Primitive a)) where
 deriving via Ranked n (Primitive Int) instance KnownINat n => Num (Ranked n Int)
 deriving via Ranked n (Primitive Double) instance KnownINat n => Num (Ranked n Double)
 
+type ListR :: Type -> INat -> Type
+data ListR i n where
+  ZR :: ListR i Z
+  (:::) :: forall n i. i -> ListR i n -> ListR i (S n)
+deriving instance Show i => Show (ListR i n)
+deriving instance Eq i => Eq (ListR i n)
+infixr 3 :::
+
 -- | An index into a rank-typed array.
 type IxR :: Type -> INat -> Type
-data IxR i n where
-  ZIR :: IxR i Z
-  (:.:) :: forall n i. i -> IxR i n -> IxR i (S n)
-deriving instance Show i => Show (IxR i n)
-deriving instance Eq i => Eq (IxR i n)
+newtype IxR i n = IxR (ListR i n)
+  deriving (Show, Eq)
+
+pattern ZIR :: forall n i. () => n ~ Z => IxR i n
+pattern ZIR = IxR ZR
+
+pattern (:.:)
+  :: forall {n1} {i}.
+     forall n. ((S n) ~ n1)
+  => i -> IxR i n -> IxR i n1
+pattern i :.: sh <- (unconsIxR -> Just (UnconsIxRRes sh i))
+  where i :.: (IxR sh) = IxR (i ::: sh)
+{-# COMPLETE ZIR, (:.:) #-}
 infixr 3 :.:
 
+data UnconsIxRRes i n1 =
+  forall n. ((S n) ~ n1) => UnconsIxRRes (IxR i n) i
+unconsIxR :: IxR i n1 -> Maybe (UnconsIxRRes i n1)
+unconsIxR (IxR sh) = case sh of
+  i ::: sh' -> Just (UnconsIxRRes (IxR sh') i)
+  ZR -> Nothing
+
 type IIxR = IxR Int
 
+type StaticShapeR :: Type -> INat -> Type
+newtype StaticShapeR i n = StaticShapeR (ListR i n)
+  deriving (Show, Eq)
+
+pattern ZSR :: forall n i. () => n ~ Z => StaticShapeR i n
+pattern ZSR = StaticShapeR ZR
+
+pattern (:$:)
+  :: forall {n1} {i}.
+     forall n. ((S n) ~ n1)
+  => i -> StaticShapeR i n -> StaticShapeR i n1
+pattern i :$: sh <- (unconsStaticShapeR -> Just (UnconsStaticShapeRRes sh i))
+  where i :$: (StaticShapeR sh) = StaticShapeR (i ::: sh)
+{-# COMPLETE ZSR, (:$:) #-}
+infixr 3 :$:
+
+data UnconsStaticShapeRRes i n1 =
+  forall n. ((S n) ~ n1) => UnconsStaticShapeRRes (StaticShapeR i n) i
+unconsStaticShapeR :: StaticShapeR i n1 -> Maybe (UnconsStaticShapeRRes i n1)
+unconsStaticShapeR (StaticShapeR sh) = case sh of
+  i ::: sh' -> Just (UnconsStaticShapeRRes (StaticShapeR sh') i)
+  ZR -> Nothing
+
 zeroIxR :: SINat n -> IIxR n
 zeroIxR SZ = ZIR
 zeroIxR (SS n) = 0 :.: zeroIxR n