From 9f5b65c2c2508fd8c852a7eef135a915eec64a57 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julien=20Valverd=C3=A9?= <julien.valverde@mailo.com>
Date: Fri, 27 Mar 2026 14:21:30 +0100
Subject: [PATCH] Add Subscribable.focusTupleAt

---
 packages/effect-lens/src/Subscribable.ts | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/packages/effect-lens/src/Subscribable.ts b/packages/effect-lens/src/Subscribable.ts
index 125198e..c88a108 100644
--- a/packages/effect-lens/src/Subscribable.ts
+++ b/packages/effect-lens/src/Subscribable.ts
@@ -36,6 +36,22 @@ export const focusArrayAt: {
     index: number,
 ): Subscribable.Subscribable<A[number], E | NoSuchElementException, R> => Subscribable.mapEffect(self, Array.get(index)))
 
+/**
+ * Narrows the focus to an indexed element of a readonly tuple.
+ */
+export const focusTupleAt: {
+    <T extends readonly [any, ...any[]], I extends number, E, R>(
+        self: Subscribable.Subscribable<T, E, R>,
+        index: I,
+    ): Subscribable.Subscribable<T[I], E, R>
+    <T extends readonly [any, ...any[]], I extends number, E, R>(
+        index: I
+    ): (self: Subscribable.Subscribable<T, E, R>) => Subscribable.Subscribable<T[I], E, R>
+} = Function.dual(2, <T extends readonly [any, ...any[]], I extends number, E, R>(
+    self: Subscribable.Subscribable<T, E, R>,
+    index: I,
+): Subscribable.Subscribable<T[I], E, R> => Subscribable.map(self, Array.unsafeGet(index)))
+
 /**
  * Narrows the focus to an indexed element of `Chunk`.
  */