beman.indices_view: A range adaptor that generates a sequence of integers from $0$ to $n - 1$

Implements: std::views::indices proposed in Add std::views::indices(n) (P3060R2).

Status: Production ready. Stable API.

License

beman.indices_view is licensed under the Apache License v2.0 with LLVM Exceptions.

Usage

#include <iostream>
#include <vector>

#include <beman/indices_view/indices.hpp>

namespace biv = beman::indices_view;

// Example given in the paper for `std::views::indices`, adapted to work with C++20.
int main() {
    std::vector rng(5, 0);

    std::cout << "[";
    bool first = true;
    for (auto i : biv::indices(std::ranges::size(rng))) {
        if (!first) {
            std::cout << ", ";
        }
        std::cout << i;
        first = false;
    }
    std::cout << "]\n";

    return 0;
}

Full runnable examples can be found in examples/.

Dependencies

Build Environment

This project requires at least the following to build:

• A C++ compiler that conforms to the C++20 standard or greater
• CMake 3.30 or later
• (Test Only) GoogleTest

You can disable building tests by setting CMake option BEMAN_INDICES_VIEW_BUILD_TESTS to OFF when configuring the project.

Supported Platforms

Compiler	Version	C++ Standards	Standard Library
GCC	16-13	C++26-C++20	libstdc++
GCC	12-11	C++23, C++20	libstdc++
Clang	22-19	C++26-C++20	libstdc++, libc++
Clang	18	C++26-C++20	libc++
Clang	18	C++23, C++20	libstdc++
Clang	17	C++26-C++20	libc++
Clang	17	C++20	libstdc++
AppleClang	latest	C++26-C++20	libc++
MSVC	latest	C++23	MSVC STL

Development

See the Contributing Guidelines.

Integrate beman.indices_view into your project

Build

You can build indices_view using a CMake workflow preset:

cmake --workflow --preset gcc-release

To list available workflow presets, you can invoke:

cmake --list-presets=workflow

For details on building beman.indices_view without using a CMake preset, refer to the Contributing Guidelines.

Installation

Vcpkg

The preferred way to install indices_view is via vcpkg. To do so, after installing vcpkg itself, you need to add support for the Beman project's vcpkg registry by configuring a vcpkg-configuration.json file (which indices_view provides).

Then, simply run vcpkg install beman-indices-view.

Manual

To install beman.indices_view globally after building with the gcc-release preset, you can run:

sudo cmake --install build/gcc-release

Alternatively, to install to a prefix, for example /opt/beman, you can run:

sudo cmake --install build/gcc-release --prefix /opt/beman

This will generate the following directory structure:

/opt/beman
├── include
│   └── beman
│       └── indices_view
│           ├── indices.hpp
│           └── ...
└── lib
    └── cmake
        └── beman.indices_view
            ├── beman.indices_view-config-version.cmake
            ├── beman.indices_view-config.cmake
            └── beman.indices_view-targets.cmake

CMake Configuration

If you installed beman.indices_view to a prefix, you can specify that prefix to your CMake project using CMAKE_PREFIX_PATH; for example, -DCMAKE_PREFIX_PATH=/opt/beman.

You need to bring in the beman.indices_view package to define the beman::indices_view CMake target:

find_package(beman.indices_view REQUIRED)

You will then need to add beman::indices_view to the link libraries of any libraries or executables that include beman.indices_view headers.

target_link_libraries(yourlib PUBLIC beman::indices_view)

Using beman.indices_view

To use beman.indices_view in your C++ project, include an appropriate beman.indices_view header from your source code.

#include <beman/indices_view/indices.hpp>

Note

beman.indices_view headers are to be included with the beman/indices_view/ prefix. Altering include search paths to spell the include target another way (e.g. #include <indices.hpp>) is unsupported.