Compile-time deduction of container closability — determining whether and how a container C can be directly constructed ("closed") from a range R. More...

#include <cstdint>
#include <ranges>
#include <type_traits>
#include <vector>
#include "jh/conceptual/container_traits.h"

Namespaces
namespace	jh::concepts
	Behavioral concept namespace of the JH Toolkit.

Concepts
concept	jh::concepts::closable_container_for
	Concept checking whether a container `C` can be directly constructed ("closed") from a range `R`.

Detailed Description

Compile-time deduction of container closability — determining whether and how a container C can be directly constructed ("closed") from a range R.

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>

This header defines the closable container model — the conceptual basis for jh::ranges::to and its companion jh::ranges::collect. It classifies all possible construction paths between a container and a range, forming the foundation for the closable_container_for concept.

Purpose

In a range pipeline, a container closable from a range means that it can be built directly via iterators or an intermediate vector bridge, without explicit element-wise insertion. This allows the to adaptor to perform efficient, single-step construction.

Design rationale

Declarative deduction: All possible constructor paths are examined at compile time via requires expressions.
Non-intrusive: No specialization or overload resolution is required on the user's part.
Deterministic: The most specific viable construction path is chosen in a strictly ordered priority chain.

Move semantics and design constraint

Directly moving (consuming) the source range is semantically invalid. This restriction aligns with the intent of std::ranges::to and with the design of jh::ranges::to:
a range adaptor must never invalidate its source by stealing its state. Instead, all construction paths are iterator-based and non-destructive, preserving the observable validity of the source range.

In the JH framework, collect and to form a two-phase adaptation model:

collect<V>() — explicitly materializes any lazy or proxy-based range into a stable, value-semantic container V.
to<C>() — constructs the final container C from that materialization.

Performance note

Although closable_container_for never performs a direct move of the source object, this design imposes no runtime penalty.
When the source range is a prvalue (e.g. produced by collect), modern C++ compilers guarantee through RVO and NRVO that the intermediate container is constructed in-place, and element-wise initialization automatically uses move semantics rather than copy.
Therefore, collect + to achieves the same runtime efficiency as a single monolithic move construction, while preserving precise and standard-compliant semantics.

Core entities

jh::concepts::detail::closable_status — enumerates all construction modes.
jh::concepts::detail::compute_closable_status<C, R> — evaluates and selects the appropriate mode at compile time.
jh::concepts::closable_container_for<C, R> — concept determining if a container is closable from a range.

Relationship with other modules

jh::ranges::to — consumes closable pairs for direct construction.
jh::ranges::collect — produces closable, value-semantic intermediates.

Note: The closable_container_for concept is purely structural: it verifies, at compile time, that a container can be safely and deterministically constructed from a range, without performing any move or mutation of the source itself.

See also: jh::ranges::collect; jh::ranges::to

Version

1.3.x

Date

Namespaces