160 lines
8.2 KiB
Markdown
160 lines
8.2 KiB
Markdown
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# MPark.Variant
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> __C++17__ `std::variant` for __C++11__/__14__/__17__
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[![release][badge.release]][release]
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[![header][badge.header]][header]
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[![travis][badge.travis]][travis]
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[![appveyor][badge.appveyor]][appveyor]
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[![license][badge.license]][license]
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[![godbolt][badge.godbolt]][godbolt]
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[![wandbox][badge.wandbox]][wandbox]
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[badge.release]: https://img.shields.io/github/release/mpark/variant.svg
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[badge.header]: https://img.shields.io/badge/single%20header-master-blue.svg
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[badge.travis]: https://travis-ci.org/mpark/variant.svg?branch=master
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[badge.appveyor]: https://ci.appveyor.com/api/projects/status/github/mpark/variant?branch=master&svg=true
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[badge.license]: https://img.shields.io/badge/license-boost-blue.svg
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[badge.godbolt]: https://img.shields.io/badge/try%20it-on%20godbolt-222266.svg
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[badge.wandbox]: https://img.shields.io/badge/try%20it-on%20wandbox-5cb85c.svg
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[release]: https://github.com/mpark/variant/releases/latest
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[header]: https://github.com/mpark/variant/blob/single-header/master/variant.hpp
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[travis]: https://travis-ci.org/mpark/variant
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[appveyor]: https://ci.appveyor.com/project/mpark/variant
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[license]: https://github.com/mpark/variant/blob/master/LICENSE.md
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[godbolt]: https://godbolt.org/z/4r7hEy
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[wandbox]: https://wandbox.org/permlink/dTZxf85MVhehOqx1
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## Introduction
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__MPark.Variant__ is an implementation of __C++17__ `std::variant` for __C++11__/__14__/__17__.
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- Based on [my implementation of `std::variant` for __libc++__][libcxx-impl]
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- Continuously tested against __libc++__'s `std::variant` test suite.
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[libcxx-impl]: https://reviews.llvm.org/rL288547
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## Documentation
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- [cppreference.com](http://en.cppreference.com/w/cpp/utility/variant)
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- [eel.is/c++draft](http://eel.is/c++draft/variant)
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## Integration
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### Single Header
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The [single-header] branch provides a standalone `variant.hpp`
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file for each [release](https://github.com/mpark/variant/releases).
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Copy it and `#include` away!
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[single-header]: https://github.com/mpark/variant/tree/single-header
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### Submodule
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You can add `mpark/variant` as a submodule to your project.
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```bash
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git submodule add https://github.com/mpark/variant.git 3rdparty/variant
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```
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Add the `include` directory to your include path with
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`-I3rdparty/variant/include` then `#include` the `variant.hpp` header
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with `#include <mpark/variant.hpp>`.
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If you use CMake, you can simply use `add_subdirectory(3rdparty/variant)`:
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```cmake
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cmake_minimum_required(VERSION 3.6.3)
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project(HelloWorld CXX)
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add_subdirectory(3rdparty/variant)
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add_executable(hello-world hello_world.cpp)
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target_link_libraries(hello-world mpark_variant)
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```
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### Installation / CMake `find_package`
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```bash
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git clone https://github.com/mpark/variant.git
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mkdir variant/build && cd variant/build
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cmake ..
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cmake --build . --target install
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```
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This will install `mpark/variant` to the default install-directory for
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your platform (`/usr/local` for Unix, `C:\Program Files` for Windows).
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You can also install at a custom location via the `CMAKE_INSTALL_PREFIX`
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variable, (e.g., `cmake .. -DCMAKE_INSTALL_PREFIX=/opt`).
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The installed `mpark/variant` can then be found by CMake via `find_package`:
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```cmake
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cmake_minimum_required(VERSION 3.6.3)
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project(HelloWorld CXX)
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find_package(mpark_variant 1.3.0 REQUIRED)
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add_executable(hello-world hello_world.cpp)
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target_link_libraries(hello-world mpark_variant)
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```
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CMake will search for `mpark/variant` in its default set of
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installation prefixes. If `mpark/variant` is installed in
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a custom location via the `CMAKE_INSTALL_PREFIX` variable,
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you'll likely need to use the `CMAKE_PREFIX_PATH` to specify
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the location (e.g., `cmake .. -DCMAKE_PREFIX_PATH=/opt`).
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## Requirements
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This library requires a standard conformant __C++11__ compiler.
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The following compilers are continously tested:
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| Compiler | Operating System | Version String |
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| -------------------------------------- | ------------------------------------------- | ---------------------------------------------------------------------------------- |
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| GCC 4.8.5 | Ubuntu 16.04.5 LTS | g++-4.8 (Ubuntu 4.8.5-4ubuntu8~16.04.1) 4.8.5 |
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| GCC 4.9.4 | Ubuntu 16.04.5 LTS | g++-4.9 (Ubuntu 4.9.4-2ubuntu1~16.04) 4.9.4 |
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| GCC 5.5.0 | Ubuntu 16.04.5 LTS | g++-5 (Ubuntu 5.5.0-12ubuntu1~16.04) 5.5.0 20171010 |
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| GCC 6.5.0 | Ubuntu 16.04.5 LTS | g++-6 (Ubuntu 6.5.0-2ubuntu1~16.04) 6.5.0 20181026 |
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| GCC 7.4.0 | Ubuntu 16.04.5 LTS | g++-7 (Ubuntu 7.4.0-1ubuntu1\~16.04\~ppa1) 7.4.0 |
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| GCC 8.1.0 | Ubuntu 16.04.5 LTS | g++-8 (Ubuntu 8.1.0-5ubuntu1~16.04) 8.1.0 |
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| Clang 3.6.2 | Ubuntu 16.04.5 LTS | Ubuntu clang version 3.6.2-3ubuntu2 (tags/RELEASE_362/final) (based on LLVM 3.6.2) |
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| Clang 3.7.1 | Ubuntu 16.04.5 LTS | Ubuntu clang version 3.7.1-2ubuntu2 (tags/RELEASE_371/final) (based on LLVM 3.7.1) |
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| Clang 3.8.0 | Ubuntu 16.04.5 LTS | clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final) |
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| Clang 3.9.1 | Ubuntu 16.04.5 LTS | clang version 3.9.1-4ubuntu3~16.04.2 (tags/RELEASE_391/rc2) |
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| Clang 4.0.0 | Ubuntu 16.04.5 LTS | clang version 4.0.0-1ubuntu1~16.04.2 (tags/RELEASE_400/rc1) |
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| Clang 5.0.0 | Ubuntu 16.04.5 LTS | clang version 5.0.0-3~16.04.1 (tags/RELEASE_500/final) |
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| Clang 6.0.0 | Ubuntu 16.04.5 LTS | clang version 6.0.0-1ubuntu2~16.04.1 (tags/RELEASE_600/final) |
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| Clang 7.0.1 | Ubuntu 16.04.5 LTS | clang version 7.0.1-svn347285-1\~exp1\~20181124105320.40 (branches/release_70) |
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| Clang Xcode 8.3 | Darwin Kernel Version 16.7.0 (OS X 10.12.6) | Apple LLVM version 8.1.0 (clang-802.0.42) |
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| Clang Xcode 9.4 | Darwin Kernel Version 17.4.0 (OS X 10.13.3) | Apple LLVM version 9.1.0 (clang-902.0.39.2) |
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| Clang Xcode 10.1 | Darwin Kernel Version 17.7.0 (OS X 10.13.6) | Apple LLVM version 10.0.0 (clang-1000.11.45.5) |
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| Visual Studio 14 2015 | Visual Studio 2015 with Update 3 | MSVC 19.0.24241.7 |
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| Visual Studio 15 2017 | Visual Studio 2017 with Update 8 | MSVC 19.15.26732.1 |
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| Visual Studio 15 2017 | Visual Studio 2017 with Update 9 | MSVC 19.16.27025.1 |
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| Visual Studio 15 2017 (__Clang/LLVM__) | Visual Studio 2017 | Clang 7.0.0 |
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#### NOTES
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- __GCC 4.8__/__4.9__: `constexpr` support is not available for `visit` and relational operators.
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- Enabling __libc++__ `std::variant` tests require `-std=c++17` support.
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## CMake Variables
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- __`MPARK_VARIANT_INCLUDE_TESTS`__:`STRING` (__default__: `""`)
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Semicolon-separated list of tests to build.
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Possible values are `mpark`, and `libc++`.
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__NOTE__: The __libc++__ `std::variant` tests are built with `-std=c++17`.
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## Unit Tests
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Refer to [test/README.md](test/README.md).
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## License
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Distributed under the [Boost Software License, Version 1.0](LICENSE.md).
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