monostate.h File Reference

Trivial placeholder type monostate and its traits. More...

#include <type_traits>

Go to the source code of this file.

Classes
struct	jh::typed::monostate
	Trivial empty type representing "no value". More...
struct	jh::typed::is_monostate< T >
	Type trait: checks whether T is monostate. More...
struct	jh::typed::is_monostate< monostate >

Namespaces
namespace	jh::typed
	Aggregated entry point for lightweight typing and semantic placeholder utilities.

Concepts
concept	jh::typed::monostate_t
	Concept: satisfied only if T is monostate.

Detailed Description

Trivial placeholder type monostate and its traits.

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 <mastropseudo@gmail.com>

Provides jh::typed::monostate, a strict POD type equivalent in spirit to std::monostate, but lightweight and header-only (no dependency on <variant> or other STL headers).

Components:

• monostate — trivial empty type with equality operators.
• is_monostate<T> — type trait for detection.
• monostate_t<T> — concept form for SFINAE/constraints.

Design Goals:

• POD compliance: trivially copyable, trivially constructible, standard layout.
• Minimal dependency footprint, no heavy STL headers required.
• Use as a safe placeholder in POD containers (e.g. unused tuple slots).

Notes:

• Represents only "no value"; not interchangeable with nullopt or nullable types.
• Has no runtime state, equality is always true.

Version

1.3.x

Date

2025