r20

Backporting C++23 Ranges to C++20

r20 is a lightweight, header-only library that backports selected C++23 <ranges> features to C++20.
It fills the gap for developers who want to use modern range adaptors and views—without requiring the full C++23 toolchain or standard library support.

✨ Features

• Backports commonly used C++23 range adaptors and utilities
  (e.g., views::chunk, views::chunk_by, views::enumerate, etc.)
• Implements missing C++20/23 range concepts where needed
• Header-only and dependency-free
• Works on major compilers supporting C++20:
  • GCC ≥ 12
  • Clang ≥ 19 (may work on Clang 16-18, but not tested)
  • MSVC (VS 2022) (Untested)

🔧 Installation

Simply add the r20 include directory to your project:

#include <rxx/ranges.h>

🧪 Testing

The comprehensive test suite for r20 is maintained in a separate repository to keep the core library lightweight. The tests are NOT supported on Windows.

👉 r20-tests Repository

Acknowledgments & Copyright

To ensure high reliability and parity with standard implementations, many tests in the suite are adapted from:

The LLVM Project (libc++): Licensed under the Apache License v2.0 with LLVM Exceptions.

GNU Toolchain (libstdc++): Licensed under the GNU General Public License v3.0 (or later) with Runtime Exceptions.

Running Tests

1. Clone the test repository.

2. Ensure you are using a supported C++20 compliant compiler.

3. Run the following

cd r20-tests
RXX_SRC=/path/to/r20/repo make -j$(nproc) all