Add Subscribable.focusTupleAt

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`.
  */