Concatenation of arrays for M and R

What should the type of sconcat be?

1 files changed, 23 insertions, 0 deletions

diff --git a/src/Data/Array/Nested/Internal/Mixed.hs b/src/Data/Array/Nested/Internal/Mixed.hs
index dcd86d1..6d601b8 100644
--- a/src/Data/Array/Nested/Internal/Mixed.hs
+++ b/src/Data/Array/Nested/Internal/Mixed.hs
@@ -18,15 +18,19 @@
 {-# LANGUAGE ViewPatterns #-}
 module Data.Array.Nested.Internal.Mixed where
 
+import Prelude hiding (mconcat)
+
 import Control.DeepSeq (NFData)
 import Control.Monad (forM_, when)
 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(..))
+import Data.List.NonEmpty qualified as NE
 import Data.Proxy
 import Data.Type.Equality
 import Data.Vector.Storable qualified as VS
@@ -280,6 +284,10 @@ class Elt a where
   mtranspose :: forall is sh. (IsPermutation is, Rank is <= Rank sh)
              => Perm is -> Mixed sh a -> Mixed (PermutePrefix is sh) a
 
+  -- | All arrays in the input must have equal shapes, including subarrays
+  -- inside their elements.
+  mconcat :: NonEmpty (Mixed (Nothing : sh) a) -> Mixed (Nothing : sh) a
+
   -- ====== PRIVATE METHODS ====== --
 
   -- | Tree giving the shape of every array component.
@@ -366,6 +374,11 @@ instance Storable a => Elt (Primitive a) where
     M_Primitive (shxPermutePrefix perm sh)
                 (X.transpose (ssxFromShape sh) perm arr)
 
+  mconcat :: forall sh. NonEmpty (Mixed (Nothing : sh) (Primitive a)) -> Mixed (Nothing : sh) (Primitive a)
+  mconcat l@(M_Primitive (_ :$% sh) _ :| _) =
+    let result = X.concat (ssxFromShape sh) (fmap (\(M_Primitive _ arr) -> arr) l)
+    in M_Primitive (X.shape (SUnknown () :!% ssxFromShape sh) result) result
+
   type ShapeTree (Primitive a) = ()
   mshapeTree _ = ()
   mshapeTreeEq _ () () = True
@@ -424,6 +437,11 @@ instance (Elt a, Elt b) => Elt (a, b) where
     M_Tup2 (mcast ssh1 sh2 psh' a) (mcast ssh1 sh2 psh' b)
 
   mtranspose perm (M_Tup2 a b) = M_Tup2 (mtranspose perm a) (mtranspose perm b)
+  mconcat =
+    let unzipT2l [] = ([], [])
+        unzipT2l (M_Tup2 a b : l) = let (l1, l2) = unzipT2l l in (a : l1, b : l2)
+        unzipT2 (M_Tup2 a b :| l) = let (l1, l2) = unzipT2l l in (a :| l1, b :| l2)
+    in uncurry M_Tup2 . bimap mconcat mconcat . unzipT2
 
   type ShapeTree (a, b) = (ShapeTree a, ShapeTree b)
   mshapeTree (x, y) = (mshapeTree x, mshapeTree y)
@@ -526,6 +544,11 @@ instance Elt a => Elt (Mixed sh' a) where
     = M_Nest (shxPermutePrefix perm sh)
              (mtranspose perm arr)
 
+  mconcat :: NonEmpty (Mixed (Nothing : sh) (Mixed sh' a)) -> Mixed (Nothing : sh) (Mixed sh' a)
+  mconcat l@(M_Nest sh1 _ :| _) =
+    let result = mconcat (fmap (\(M_Nest _ arr) -> arr) l)
+    in M_Nest (fst (shxSplitApp (Proxy @sh') (ssxFromShape sh1) (mshape result))) result
+
   type ShapeTree (Mixed sh' a) = (IShX sh', ShapeTree a)
 
   mshapeTree :: Mixed sh' a -> ShapeTree (Mixed sh' a)