beman.span: A Beman implementation of std::span

beman.span is an implementation of various proposed updates to std::span.

Implements: std::span a non-owning view over a contiguous sequence of objects. See cppreference — std::span and eel.is/c++draft/views.span.

Status: Under development and not yet ready for production use.

License

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

Features

• Header-only, no external runtime dependencies
• Supports both fixed and dynamic extents (beman::span::dynamic_extent)
• Full constructor overloads: C-array, std::array, pointer+count, pointer pair, generic range
• Subviews: first(), last(), subspan() both compile-time and runtime versions
• Object representation helpers: as_bytes(), as_writable_bytes()
• Deduction guides (C++17)
• constexpr throughout
• Compared with std::span in tests when available (__cpp_lib_span)

Usage

#include <beman/span/span.hpp>

#include <array>
#include <vector>
#include <iostream>

namespace bsp = beman::span;

void print(bsp::span<const int> s) {
    for (auto v : s)
        std::cout << v << ' ';
    std::cout << '\n';
}

int main() {
    // From a C-array (fixed extent deduced)
    int arr[] = {1, 2, 3, 4, 5};
    bsp::span s1(arr);           // span<int, 5>
    print(s1);

    // From a vector (dynamic extent)
    std::vector<int> v = {10, 20, 30};
    bsp::span<int> s2(v);
    print(s2.first(2));          // span<int, dynamic_extent> {10, 20}

    // Byte view
    auto bytes = bsp::as_bytes(s1);
    std::cout << "size_bytes=" << bytes.size() << '\n';
}

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_SPAN_BUILD_TESTS to OFF when configuring the project.

Supported Platforms

Compiler	Version	C++ Standards	Standard Library
GCC	15-13	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.span into your project

Build

You can build span 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.span without using a CMake preset, refer to the Contributing Guidelines.

Installation

Vcpkg

The preferred way to install span 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 span provides).

Then, simply run vcpkg install beman-span.

Manual

To install beman.span 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
│       └── span
│           ├── span.hpp
│           └── ...
└── lib
    └── cmake
        └── beman.span
            ├── beman.span-config-version.cmake
            ├── beman.span-config.cmake
            └── beman.span-targets.cmake

CMake Configuration

If you installed beman.span 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.span package to define the beman::span CMake target:

find_package(beman.span REQUIRED)

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

target_link_libraries(yourlib PUBLIC beman::span)

Using beman.span

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

#include <beman/span/span.hpp>

Note

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