From c817dc656a37a8f4e73234a8387ff3e3242ba24e Mon Sep 17 00:00:00 2001
From: Henri Binsztok <808274+hbbio@users.noreply.github.com>
Date: Mon, 5 Feb 2024 15:36:35 +0800
Subject: [PATCH 1/2] cell: update directly from a pointer

---
 src/cell.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/cell.ts b/src/cell.ts
index d9ab3ee..b9a670d 100644
--- a/src/cell.ts
+++ b/src/cell.ts
@@ -779,7 +779,11 @@ export class ValueCell<V> extends Cell<V, false, false> {
   update = (
     fn: (v: V) => V | Promise<V> | AnyCell<V> | Promise<AnyCell<V>>
   ) => {
-    if (this.isPointer) throw this.newError("Cell is a pointer");
+    if (this.isPointer) {
+      const cell = this._sheet.get(this.pointed);
+      if (cell instanceof ValueCell) return cell.update(fn);
+      throw this.newError("Cell is a pointer to a MapCell");
+    }
     // this line is here to help the typechecker
     //@ts-expect-error isPointer rules out AnyCell
     const v: V | Error | undefined = this.v;

From 94d36523301aca05ec6e91ae7597bc2f87247359 Mon Sep 17 00:00:00 2001
From: Henri Binsztok <808274+hbbio@users.noreply.github.com>
Date: Mon, 5 Feb 2024 15:55:15 +0800
Subject: [PATCH 2/2] pointers: test update from pointer

---
 src/pointers.test.ts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/pointers.test.ts b/src/pointers.test.ts
index 30bdbe5..435774c 100644
--- a/src/pointers.test.ts
+++ b/src/pointers.test.ts
@@ -318,3 +318,12 @@ test("get pointer chain", async () => {
   const m2 = m.map((v) => delayed(m, 20));
   await expect(m2.get()).resolves.toBe(2);
 });
+
+test("update from pointer", async () => {
+  const proxy = new Sheet().newProxy();
+  const v = proxy.new(1);
+  const p = proxy.new(v);
+  p.update((x) => x + 1);
+  await expect(v.get()).resolves.toBe(2);
+  await expect(p.get()).resolves.toBe(2);
+});