diff --git a/src/Data/NumIdr/Array/Array.idr b/src/Data/NumIdr/Array/Array.idr
index faad3e9..cbbbfc6 100644
--- a/src/Data/NumIdr/Array/Array.idr
+++ b/src/Data/NumIdr/Array/Array.idr
@@ -83,11 +83,6 @@ rank : Array s a -> Nat
 rank = length . shape
 
 
-export
-shapeEq : (arr : Array s a) -> s = shape arr
-shapeEq (MkArray _ _ _ _) = Refl
-
-
 -- Get a list of all coordinates
 getAllCoords' : Vect rk Nat -> List (Vect rk Nat)
 getAllCoords' = traverse (\case Z => []; S n => [0..n])
@@ -103,11 +98,16 @@ getAllCoords (S d :: s) = [| forget (allFins d) :: getAllCoords s |]
 --------------------------------------------------------------------------------
 
 
+export
+shapeEq : (arr : Array s a) -> s = shape arr
+shapeEq (MkArray _ _ _ _) = Refl
+
+
 public export
 data ShapeView : Array s a -> Type where
   Shape : (s : Vect rk Nat) -> {0 arr : Array s a} -> ShapeView arr
 
-public export
+export
 viewShape : (arr : Array s a) -> ShapeView arr
 viewShape arr = rewrite shapeEq arr in
                   Shape (shape arr)
@@ -233,15 +233,36 @@ export
 (!!) : Array s a -> Coords s -> a
 (!!) = flip index
 
+-- TODO: Create set/update at index functions
+
+export
+indexUpdate : Coords s -> (a -> a) -> Array s a -> Array s a
+indexUpdate is f (MkArray ord sts s arr) = MkArray ord sts s (updateAt (getLocation sts is) f arr)
+
+export
+indexSet : Coords s -> a -> Array s a -> Array s a
+indexSet is = indexUpdate is . const
+
 
 export
 indexMaybe : Vect rk Nat -> Array {rk} s a -> Maybe a
-indexMaybe is arr = safeIndex (getLocation' (strides arr) is) (getPrim arr)
+indexMaybe is arr with (viewShape arr)
+  _ | Shape s = if concat @{All} $ zipWith (<) s (shape arr)
+                then Just $ index (getLocation' (strides arr) is) (getPrim arr)
+                else Nothing
 
 export
 (!?) : Array {rk} s a -> Vect rk Nat -> Maybe a
 (!?) = flip indexMaybe
 
+export
+indexUpdateMaybe : Vect rk Nat -> (a -> a) -> Array {rk} s a -> Array s a
+indexUpdateMaybe is f (MkArray ord sts s arr) = MkArray ord sts s (updateAt (getLocation' sts is) f arr)
+
+export
+indexSetMaybe : Vect rk Nat -> a -> Array {rk} s a -> Array s a
+indexSetMaybe is = indexUpdateMaybe is . const
+
 
 ||| Index the array using the given `CoordsRange` object.
 export
@@ -297,6 +318,10 @@ reorder ord' arr with (viewShape arr)
                       getAllCoords' s)
 
 
+export
+resize : (s' : Vect rk Nat) -> a -> Array {rk} s a -> Array s' a
+resize s' x arr = fromFunction' s' (getOrder arr) (fromMaybe x . (arr !?) . toNats)
+
 export
 enumerate' : Array {rk} s a -> List (Vect rk Nat, a)
 enumerate' (MkArray _ sts sh p) =
diff --git a/src/Data/NumIdr/Matrix.idr b/src/Data/NumIdr/Matrix.idr
index c1559da..17feb04 100644
--- a/src/Data/NumIdr/Matrix.idr
+++ b/src/Data/NumIdr/Matrix.idr
@@ -105,7 +105,5 @@ hconcat = concat 1
 
 export
 kronecker : Num a => Vector m a -> Vector n a -> Matrix m n a
-kronecker a b = rewrite dimEq a in rewrite dimEq b in
-                fromFunction [dim a, dim b]
-                  (\[i,j] => Vector.index (rewrite dimEq a in i) a *
-                             Vector.index (rewrite dimEq b in j) b)
+kronecker a b with (viewShape a, viewShape b)
+  _ | (Shape [m], Shape [n]) = fromFunction [m,n] (\[i,j] => index i a * index j b)
diff --git a/src/Data/NumIdr/PrimArray.idr b/src/Data/NumIdr/PrimArray.idr
index c7247ee..f484364 100644
--- a/src/Data/NumIdr/PrimArray.idr
+++ b/src/Data/NumIdr/PrimArray.idr
@@ -59,7 +59,6 @@ create size f = unsafePerformIO $ do
         = do arrayDataSet loc (f loc) arr
              addToArray (S loc) n arr
 
-
 ||| Index into a primitive array. This function is unsafe, as it
 ||| performs no boundary check on the index given.
 export
@@ -73,6 +72,18 @@ safeIndex n arr = if n < length arr
                 then Just $ index n arr
                 else Nothing
 
+export
+copy : PrimArray a -> PrimArray a
+copy arr = create (length arr) (\n => index n arr)
+
+export
+updateAt : Nat -> (a -> a) -> PrimArray a -> PrimArray a
+updateAt n f arr = if n >= length arr then arr else
+  unsafePerformIO $ do
+    let cpy = copy arr
+    x <- arrayDataGet n cpy.content
+    arrayDataSet n (f x) cpy.content
+    pure cpy
 
 ||| Convert a primitive array to a list.
 export