fix: doc and tests

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

v2/readeroption/sequence.go

@@ -0,0 +1,127 @@
+// Copyright (c) 2023 - 2025 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readeroption
+
+import (
+	G "github.com/IBM/fp-go/v2/readeroption/generic"
+	T "github.com/IBM/fp-go/v2/tuple"
+)
+
+// SequenceT functions convert multiple ReaderOption values into a single ReaderOption containing a tuple.
+// If any input is None, the entire result is None.
+// Otherwise, returns Some containing a tuple of all the unwrapped values.
+//
+// These functions are useful for combining multiple independent ReaderOption computations
+// where you need to preserve the individual types of each result.
+
+// SequenceT1 converts a single ReaderOption into a ReaderOption of a 1-tuple.
+// This is mainly useful for consistency with the other SequenceT functions.
+//
+// Example:
+//
+//	type Config struct { ... }
+//
+//	user := readeroption.Of[Config](User{Name: "Alice"})
+//	result := readeroption.SequenceT1(user)
+//	// result(config) returns option.Some(tuple.MakeTuple1(User{Name: "Alice"}))
+func SequenceT1[E, A any](a ReaderOption[E, A]) ReaderOption[E, T.Tuple1[A]] {
+	return G.SequenceT1[
+		ReaderOption[E, A],
+		ReaderOption[E, T.Tuple1[A]],
+	](a)
+}
+
+// SequenceT2 combines two ReaderOption values into a ReaderOption of a 2-tuple.
+// If either input is None, the result is None.
+//
+// Example:
+//
+//	type Config struct { ... }
+//
+//	user := readeroption.Of[Config](User{Name: "Alice"})
+//	count := readeroption.Of[Config](42)
+//
+//	result := readeroption.SequenceT2(user, count)
+//	// result(config) returns option.Some(tuple.MakeTuple2(User{Name: "Alice"}, 42))
+//
+//	noneUser := readeroption.None[Config, User]()
+//	result2 := readeroption.SequenceT2(noneUser, count)
+//	// result2(config) returns option.None[tuple.Tuple2[User, int]]()
+func SequenceT2[E, A, B any](
+	a ReaderOption[E, A],
+	b ReaderOption[E, B],
+) ReaderOption[E, T.Tuple2[A, B]] {
+	return G.SequenceT2[
+		ReaderOption[E, A],
+		ReaderOption[E, B],
+		ReaderOption[E, T.Tuple2[A, B]],
+	](a, b)
+}
+
+// SequenceT3 combines three ReaderOption values into a ReaderOption of a 3-tuple.
+// If any input is None, the result is None.
+//
+// Example:
+//
+//	type Config struct { ... }
+//
+//	user := readeroption.Of[Config](User{Name: "Alice"})
+//	count := readeroption.Of[Config](42)
+//	active := readeroption.Of[Config](true)
+//
+//	result := readeroption.SequenceT3(user, count, active)
+//	// result(config) returns option.Some(tuple.MakeTuple3(User{Name: "Alice"}, 42, true))
+func SequenceT3[E, A, B, C any](
+	a ReaderOption[E, A],
+	b ReaderOption[E, B],
+	c ReaderOption[E, C],
+) ReaderOption[E, T.Tuple3[A, B, C]] {
+	return G.SequenceT3[
+		ReaderOption[E, A],
+		ReaderOption[E, B],
+		ReaderOption[E, C],
+		ReaderOption[E, T.Tuple3[A, B, C]],
+	](a, b, c)
+}
+
+// SequenceT4 combines four ReaderOption values into a ReaderOption of a 4-tuple.
+// If any input is None, the result is None.
+//
+// Example:
+//
+//	type Config struct { ... }
+//
+//	user := readeroption.Of[Config](User{Name: "Alice"})
+//	count := readeroption.Of[Config](42)
+//	active := readeroption.Of[Config](true)
+//	score := readeroption.Of[Config](95.5)
+//
+//	result := readeroption.SequenceT4(user, count, active, score)
+//	// result(config) returns option.Some(tuple.MakeTuple4(User{Name: "Alice"}, 42, true, 95.5))
+func SequenceT4[E, A, B, C, D any](
+	a ReaderOption[E, A],
+	b ReaderOption[E, B],
+	c ReaderOption[E, C],
+	d ReaderOption[E, D],
+) ReaderOption[E, T.Tuple4[A, B, C, D]] {
+	return G.SequenceT4[
+		ReaderOption[E, A],
+		ReaderOption[E, B],
+		ReaderOption[E, C],
+		ReaderOption[E, D],
+		ReaderOption[E, T.Tuple4[A, B, C, D]],
+	](a, b, c, d)
+}