Unified transform adaptor that dispatches between std::views::transform and jh::ranges::views::vis_transform. More...

#include "jh/ranges/views/vis_transform.h"

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::transform_fn	jh::ranges::views::transform {}
	The unified `transform` adaptor entry point.

Detailed Description

Unified transform adaptor that dispatches between std::views::transform and jh::ranges::views::vis_transform.

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

The jh::ranges::views::transform adaptor performs a compile-time semantic dispatch between two transformation behaviors:

jh::ranges::views::vis_transform — when the pair <R, F> satisfies jh::concepts::vis_function_for, meaning the range is non-consuming and the function is a pure observation (returns non-void).
std::views::transform — otherwise, for standard consumptive transformations that may alter or terminate the underlying stream.

Problem: std::views::transform treats every projection as consumptive, even when it merely observes elements. This breaks reentrancy and forces intermediate buffering in non-consuming pipelines.
Solution: Defer dispatch until both R and F are known, so the adaptor can route to vis_transform only when the combination preserves observation semantics. This ensures correctness and efficiency.

Supports both direct and pipe usage forms:

Note: Dispatch occurs inside the call operator, because determining whether vis_transform semantics apply requires both the range and the callable type. This ensures that only non-consuming, pure-observation combinations are elevated to vis_transform, while all others fall back to the standard std::views::transform.

See also: jh::concepts::vis_function_for; jh::ranges::views::vis_transform; std::views::transform

Version

1.3.x

Date

Namespaces