From ee3c942c9d3b4964793b473dd5afcca9e3079283 Mon Sep 17 00:00:00 2001
From: Dri3xCz <Dri3xCz@gmail.com>
Date: Mon, 16 Feb 2026 23:35:14 +0100
Subject: [PATCH] feat: zip method on Either to "zip" two eithers into a tuple,
 right-biased

---
 lib/src/either.dart   |  2 ++
 test/either_test.dart | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/lib/src/either.dart b/lib/src/either.dart
index 2ee5b58..9d07a3e 100644
--- a/lib/src/either.dart
+++ b/lib/src/either.dart
@@ -139,6 +139,8 @@ abstract class Either<L, R> implements TraversableMonadOps<Either<L, dynamic>, R
 
   @override Either<L, Tuple2<int, R>> zipWithIndex() => map((r) => tuple2(0, r));
 
+  Either<L, Tuple2<R, RB>> zip<RB>(Either<L, RB> eitherB) => flatMap((a) => eitherB.map((b) => tuple2(a, b)));
+
   @override bool all(bool f(R r)) => map(f)|true;
   @override bool every(bool f(R r)) => all(f);
 
diff --git a/test/either_test.dart b/test/either_test.dart
index 6461710..b1f7c5f 100644
--- a/test/either_test.dart
+++ b/test/either_test.dart
@@ -103,4 +103,18 @@ void main() {
       expect(right.value, 2);
     });
   });
+
+  group("zip", () {
+    test('value', () {
+      final r1 = right<String, int>(1);
+      final r2 = right<String, int>(2);
+      final l1 = left<String, int>("foo");
+      final l2 = left<String, int>("bar");
+
+      expect(r1.zip(r2), right(tuple2(1, 2)));
+      expect(r1.zip(l1), left("foo"));
+      expect(r1.zip(l2), left("bar"));
+      expect(l1.zip(r2), left("foo"));
+    });
+  });
 }