common.h File Reference

A unified common view adaptor for both std::ranges::range and jh::concepts::sequence types. More...

#include <ranges>
#include "jh/conceptual/sequence.h"

Go to the source code of this file.

Namespaces
namespace	jh::ranges
	Semantic pipeline namespace for JH range operations.
namespace	jh::ranges::views
	Range view adaptor implementations with explicit semantic control.

Variables
constexpr detail::common_fn	jh::ranges::views::common {}
	User-facing common adaptor instance.

Detailed Description

A unified common view adaptor for both std::ranges::range and jh::concepts::sequence types.

Copyright

Copyright 2025 JeongHan-Bae <mastropseudo@gmail.com>
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.

Full license: GitHub

Author

JeongHan-Bae mastr.nosp@m.opse.nosp@m.udo@g.nosp@m.mail.nosp@m..com

This header provides jh::ranges::views::common — a lightweight and compatible wrapper around the standard std::views::common adaptor (C++20). It extends the adaptor to support any type modeling jh::concepts::sequence, enabling third-party or user-defined sequence types to interoperate naturally with the standard range pipeline.

The adaptor normalizes iterator/sentinel categories without altering data ownership semantics. For standard ranges, it behaves identically to std::views::common. For types satisfying jh::concepts::sequence, it performs a promotion through jh::to_range() to obtain a valid range representation. Non-copyable or non-movable sequences are automatically proxied via std::ranges::subrange when required.

Behavior summary:

• If the source models jh::concepts::sequence, it is promoted using jh::to_range() and wrapped by std::ranges::common_view.
• If the source models only std::ranges::range, the adaptor forwards to std::views::common().
• Existing common_range types remain unchanged, except when proxied for non-copyable sources.

Usage examples:

using namespace jh::ranges::views;
 
// 1. Standard range usage
auto v1 = std::views::iota(0, 5) | common();
// equivalent to std::views::common(iota(...))
 
// 2. A user-defined type modeling jh::concepts::sequence
MySequence seq = ...;        // satisfies jh::concepts::sequence
auto v2 = seq | common();
// promoted through jh::to_range() and std::views::common()
 
// 3. A non-copyable but reentrant range
jh::runtime_arr<int> arr{1, 2, 3};
auto v3 = arr | common();
// already a common_range; produces a subrange proxy if needed
 
// 4. Composed pipeline example
auto combined =
    ids | enumerate(100)
        | zip_pipe(names)
        | flatten()
        | common();

Notes:

• Applying common() to a temporary object results in a dangling view. Always ensure the source object outlives the resulting view.
• If the input already models std::ranges::common_range, common() performs no semantic change; it may return a subrange proxy for non-copyable or non-movable sources.
• For consuming (single-pass) ranges, the adaptor directly invokes std::views::common().

Version

1.3.x

Date

2025