range-v3

Range library for C++14/17/20. This code was the basis of a formal proposal to add range support to the C++ standard library. That proposal evolved through a Technical Specification, and finally into P0896R4 "The One Ranges Proposal" which was merged into the C++20 working drafts in November 2018.

About:

Ranges are an extension of the Standard Template Library that makes its iterators and algorithms more powerful by making them composable. Unlike other range-like solutions which seek to do away with iterators, in range-v3 ranges are an abstraction layer on top of iterators.

Range-v3 is built on three pillars: Views, Actions, and Algorithms. The algorithms are the same as those with which you are already familiar in the STL, except that in range-v3 all the algorithms have overloads that take ranges in addition to the overloads that take iterators. Views are composable adaptations of ranges where the adaptation happens lazily as the view is iterated. And an action is an eager application of an algorithm to a container that mutates the container in-place and returns it for further processing.

Views and actions use the pipe syntax (e.g., rng | adapt1 | adapt2 | ...) so your code is terse and readable from left to right.

Documentation:

Check out the (woefully incomplete) documentation here.

Other resources (mind the dates, the library probably has changed since then):

• Usage:

  • Talk: CppCon 2015: Eric Niebler "Ranges for the Standard Library", 2015.
  • A slice of Python in C++, 07.12.2014.
  • Actions (back then called Container Algorithms), 23.11.2014.
  • Range comprehensions, 27.04.2014.
  • Input iterators vs input ranges, 07.11.2013.

• Design / Implementation:

  • Rationale behind range-v3: N4128: Ranges for the standard library Revision 1, 2014.
  • Ranges TS: N4560: C++ Extensions for Ranges, 2015.
  • Implementation of customization points in range-v3:
    • N4381: Suggested Design for Customization Points, 2015.
    • P0386: Inline variables, 2016.
    • Customization Point Design in C++11 and Beyond, 2014.
  • Proxy iterators in range-v3:
    • D0022: Proxy Iterators for the Ranges Extensions.
    • To Be or Not to Be (an Iterator), 2015.
    • Iterators++: Part1, 2015.
    • Iterators++: Part2, 2015.
    • Iterators++: Part3, 2015.
  • Metaprogramming utilities:
    • See the meta documentation, the library has changed significantly since the 2014 blog post.
  • Concept emulation layer: Concept checking in C++11, 2013.
  • C++Now 2014: Eric Niebler "C++11 Library Design", 2014.

License:

Most of the source code in this project are mine, and those are under the Boost Software License. Parts are taken from Alex Stepanov's Elements of Programming, Howard Hinnant's libc++, and from the SGI STL. Please see the attached LICENSE file and the CREDITS file for the licensing and acknowledgments.

Supported Compilers

The code is known to work on the following compilers:

• clang 5.0 (or later)
• GCC 6.5 (or later)
• Clang/LLVM 6 (or later) on Windows (older versions may work - we haven't tested.)
• Visual Studio 2019 (or later) on Windows, with some caveats due to range-v3's strict conformance requirements:
  • range-v3 needs /permissive- and either /std:c++latest, /std:c++20, or /std:c++17

Development Status: This code is fairly stable, well-tested, and suitable for casual use, although currently lacking documentation. In general, no promise is made about support or long-term stability. This code will evolve without regard to backwards compatibility.

A notable exception is anything found within the ranges::cpp20 namespace. Those components will change rarely or (preferably) never at all.

Build status

• on GitHub Actions:

Building range-v3 - Using vcpkg

You can download and install range-v3 using the vcpkg dependency manager:

git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install range-v3

The range-v3 port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.

Building range-v3 - Using Conan

You can download and install range-v3 using the Conan dependency manager.

Setup your CMakeLists.txt (see Conan documentation on how to use MSBuild, Meson and others):

project(myproject CXX)

add_executable(${PROJECT_NAME} main.cpp)

include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake) # Include Conan-generated file
conan_basic_setup(TARGETS) # Introduce Conan-generated targets

target_link_libraries(${PROJECT_NAME} CONAN_PKG::range-v3)

Create conanfile.txt in your source dir:

[requires]
range-v3/0.12.0

[generators]
cmake

Install and run conan, then build your project as always:

pip install conan
mkdir build
cd build
conan install ../ --build=missing
cmake ../
cmake --build .

Building range-v3 - Using build2

You can use build2, a dependency manager and build-system combined, to use range-v3 (or work on it):

Currently this package is available in these package repositories:

• https://cppget.org/range-v3/ for released and published versions.
• The git repository with the sources of the build2 package of range-v3 for unreleased or custom revisions of range-v3, or for working on it with build2.

Usage:

• build2 package name: range-v3
• Library target name : lib{range-v3}
• Detailed use cases and instructions in this document.

For example, to make your build2 project depend on range-v3:

• Add one of the repositories to your configurations, or in your repositories.manifest, if not already there; for example:

  :
  role: prerequisite
  location: https://pkg.cppget.org/1/alpha # v0.11.0 is there.
  

• Add this package as a dependency to your manifest file (example for v0.11.x):

  depends: range-v3 ~0.11.0
  

• Import the target and use it as a prerequisite to your own target using range-v3 in the appropriate buildfile:

  import range_v3 = range-v3%lib{range-v3}
  
  lib{mylib} : cxx{**} ... $range_v3

Then just build your project as usual (with b or bdep update), build2 will figure out the rest.

For build2 newcomers or to get more details and use cases, you can read this document and the build2 toolchain introduction.