1 files changed, 42 insertions, 2 deletions
diff --git a/dynarray.sml b/dynarray.sml
index d52f148..4e64461 100644
--- a/dynarray.sml
+++ b/dynarray.sml
@@ -89,9 +89,49 @@ structure Dynarray: DYNARRAY = struct
     fun loop idx =
       if idx = len then
         ()
-      else
-        f (idx, valOf $ Array.sub (arr, idx))
+      else (
+        f (idx, valOf $ Array.sub (arr, idx));
+        loop (idx + 1)
+      )
   in
     loop 0
   end
+
+  fun last dynarr =
+  let
+    val len = length dynarr
+  in
+    get dynarr (len - 1)
+  end
+
+  fun pop dynarr =
+  let
+    val v = last dynarr
+    val (len, arr) = !dynarr
+  in
+    dynarr := (len - 1, arr);
+    v
+  end
+
+  fun update dynarr f id =
+  let
+    val v = get dynarr id
+    val v = f v
+  in
+    set dynarr id v
+  end
+
+  fun copy (dynarr: 'a t) (f: 'a -> 'b): 'b t =
+  let
+    val dynarr2 = create (length dynarr)
+
+    fun loop idx =
+      if idx = length dynarr then
+        ()
+      else
+        (push dynarr2 (f $ get dynarr idx); loop (idx + 1))
+  in
+    loop 0;
+    dynarr2
+  end
 end