Update docs

packages/example/src/quickstart.ts

@@ -1,5 +1,5 @@
 import { KeyValueStore } from "@effect/platform"
-import { Array, Console, Effect, Stream, SubscriptionRef } from "effect"
+import { Array, Console, DateTime, Effect, Stream, SubscriptionRef } from "effect"
 import { Lens } from "effect-lens"
 
 Effect.gen(function*() {
@@ -17,7 +17,38 @@ Effect.gen(function*() {
 })
 
 Effect.gen(function*() {
-    const lens = Lens.make({
-        get: Effect.andThen(KeyValueStore.KeyValueStore, )
+    interface User {
+        readonly name: string
+        readonly age: DateTime.Utc
+    }
+
+    // The state of your app
+    const ref = yield* SubscriptionRef.make<{
+        readonly users: readonly User[]
+    }>({
+        users: [
+            { name: "Jean Dupont", age: yield* DateTime.make("03/25/1969") },
+            { name: "Juan Joya Borja", age: yield* DateTime.make("04/05/1956") },
+            { name: "Benzemonstre", age: yield* DateTime.make("06/12/2000") },
+        ]
     })
-})
+
+    //                \/ Lens<User, NoSuchElementException, NoSuchElementException, never, never>
+    const jeanDupontLens = ref.pipe(
+        Lens.fromSubscriptionRef,  // Creates a lens that proxies the ref
+        Lens.focusField("users"),  // Creates a focused lens that points to the user field
+        Lens.focusArrayAt(0),      // Creates a focused lens that points to the first entry of the user array
+    )
+    // Reading or writing from this lense can fail with NoSuchElementException
+    // This is because of Lens.focusArrayAt(0), as reading and writing to an array can be an unsafe operation
+
+    const jeanDupont = yield* Lens.get(jeanDupontLens)
+
+    yield* Lens.set(
+        // You can focus even further down
+        Lens.focusField(jeanDupontLens, "age"),
+        yield* DateTime.make("03/25/1970"),
+    )
+    // Mutations with the parent state are performed immutably by default
+    // unless you use a specific mutable transform such as 'focusMutableField'
+})