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https://github.com/clemapfel/jluna

Julia Wrapper for C++ with Focus on Safety, Elegance, and Ease of Use
https://github.com/clemapfel/jluna

cpp cpp20 julia julia-language julia-wrapper julialang language-interface modern-cpp wrapper wrapper-api wrapper-library

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Julia Wrapper for C++ with Focus on Safety, Elegance, and Ease of Use

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README 

        
# jluna: A modern Julia Wrapper for C++ (v1.0.0)



![](./header.png)



Julia is a beautiful language, it is well-designed, and well-documented. Julia's C-API is also well-designed, less beautiful, and much less... documented.


jluna aims to fully wrap the official Julia C-API, replacing it in projects with C++ as the host language, by making accessing Julia's unique strengths through C++ safe, hassle-free, and just as beautiful.



---



### Table of Contents



0. [Introduction](README.md)

1. [Features](#features)


2. [Showcase](#showcase)


3. [Documentation](#documentation)


4. [Dependencies](#dependencies)


   4.1 [Julia 1.7.0+](#dependencies)


   4.2 [Supported Compilers: g++, clang++, MSVC](#dependencies)


   4.3 [CMake 3.12+](#dependencies)


5. [Installation](#installation--troubleshooting)


6. [License](#license)

7. [Authors](#credits)



---



### Anouncements



> **Note**: jluna is currently **not available for Apple aarch64 architectures**, such as those used by the M1 or M2 MacBooks. See [here](https://github.com/Clemapfel/jluna/issues/64) for more information. jluna should still work for Windows 10, 11, Linux, and FreeBSD.



---



### Features



+ expressive, generic syntax

+ create / call / assign Julia-side variables from C++

+ full exception forwarding, verbose error messages with complete stacktrace

+ `std` types & usertypes can be moved freely between Julia and C++

+ call arbitrary C++ functions from Julia

+ multidimensional, iterable array interface

+ provides a custom thread pool that, [unlike the C-API](https://clemens-cords.com/jluna/multi_threading.html), allows for concurrent interfacing with Julia

+ provides < 5% overhead functions, viable in performance-critical environments

+ complete [manual](https://clemens-cords.com/jluna/basics.html), [installation guide](https://clemens-cords.com/jluna/installation.md), [benchmark analysis](https://clemens-cords.com/jluna/benchmarks.html), inline documentation for IDEs - all written by a human

+ and more!



---



### Showcase



(If you are looking for examples showing best-practice basic usage, please instead consult the [manual](https://clemens-cords.com/jluna/basics.html))



#### Executing Julia Code



```cpp

 // execute multi-line Julia code

 Main.safe_eval(R"(

     f(x) = x^x^x

     vec = Int64[1, 2, 3, 4]

 )");



 // call Julia functions with C++ values

 auto f = Main["f"];

 std::cout << (Int64) f(3) << std::endl;



 // mutate Julia-side values

 Main["vec"][2] = 999;

 Main.safe_eval("println(vec)");



 // assign `std` objects to Julia variables

 Main["vec"] = std::vector{117, 118, 119, 120};

 Main.safe_eval("println(vec)");

```

```

2030534587

[1, 2, 999, 4]

['u', 'v', 'w', 'x']

```



---



#### Array Interface



```cpp

// array interface

Array matrix = Main.safe_eval("return reshape([i for i in 1:(4*4)], 4, 4)");



// supports multi-dimensional indexing (and array comprehension, not shown here)

matrix.at(0, 2) = 999;

Main["println"](matrix);



// even has generator expressions!

auto generated_vector = Vector("(Char(i) for i in 97:104)"_gen);

Main["println"](generated_vector);

```

```

[1 5 9 13; 2 6 10 14; 999 7 11 15; 4 8 12 16]

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

```



---



#### Calling C++ Functions from Julia

```cpp

Main.safe_eval("cpp_function = () -> ()"); // forward declaration



// assign C++ lambda to Julia Function

Main["cpp_function"] = as_julia_function(

    [](std::string in) -> void {

        std::cout << "cpp prints: " << in << std::endl;

    }

);



// call lambda, entirely Julia-side

Main.safe_eval(R"(

  cpp_function("what_julia_hands_it")

)");

```

```

cpp prints: what_julia_hands_it

```

---



## Documentation



Documentation, including a step-by-step installation and troubleshooting guide, tutorial, and index of all functions and objects in jluna is available

[here](https://clemens-cords.com/jluna).



---



## Dependencies



jluna aims to be as modern as is practical. It uses C++20 features extensively and aims to support the newest Julia version, rather than focusing on backwards compatibility.



For jluna you'll need:

+ [**Julia 1.7.0**](https://julialang.org/downloads/#current_stable_release) (or newer)

+ [**cmake 3.12**](https://cmake.org/download/) (or newer)

+ C++ Compiler, one of

  - [g++10](https://gcc.gnu.org/) (or newer)
 

  - [clang++-12](https://releases.llvm.org/) (or newer)
 

  - [MSVC](https://visualstudio.microsoft.com/downloads/) 19.34 (or newer)



On Unix, g++ or clang (installed using your package manager) are recommended. 


On Windows, either use g++ provided by [MinGW](https://sourceforge.net/projects/mingw/) or MSVC provided by the [Visual Studio C++ build tools](https://visualstudio.microsoft.com/downloads/).



In either case, make sure the compilers' version is as stated above, as jluna uses modern C++20 features extensively.



---



## [Installation & Troubleshooting](https://clemens-cords.com/jluna/installation.html)



> A step-by-step guide is available [here](https://clemens-cords.com/jluna/installation.html). It is recommended that you follow this guide, instead of the highly abridged version below.



> **For IDEs**: In many cases, simply opening the cloned jluna project in an IDE (such as VisualStudio, Atom, or CLion) will allow it to automatically set everything up for you. After initialization, simply run "install" from your build menu.



### Command Line



Execute, in your bash console, in any public directory:



```bash

git clone https://github.com/Clemapfel/jluna

cd jluna

mkdir build

cd build

```

```

cmake .. -DJULIA_BINDIR=$(julia -e "println(Sys.BINDIR)") -DCMAKE_CXX_COMPILER= -DCMAKE_INSTALL_PREFIX=

```

Where

+ `` is the C++ compiler executable, e.g. `g++`, `clang++`, `cl.exe`, etc.

+ `` is the desired install directory, omit this option to use the systems default directory



Then:

```

make install

ctest --verbose

```



Which will deposit the library to the specified system folder and run tests to make sure everything works.



#### Example Usage



For example, installing on a linux machine using g++:



```

git clone https://github.com/Clemapfel/jluna

cd jluna

mkdir build

cd build

cmake .. -DJULIA_BINDIR=$(julia -e "println(Sys.BINDIR)") -DCMAKE_CXX_COMPILER=/usr/bin/g++

sudo make install

ctest --verbose

```

Where ommitting `DCMAKE_INSTALL_PATH` makes CMake choose the default system path. `sudo` was necessary to write to that path.



---



Afterward, you can make jluna available to your library using



```cmake

# inside your own CMakeLists.txt

find_library(jluna REQUIRED 

    NAMES jluna

    PATHS 

)

target_link_libraries( PRIVATE

    "${jluna}" 

    "${}")

```

Where

+ `` is the directory specified via `-DCMAKE_INSTALL_PREFIX`

+ `` is the Julia shared library (usually available in `"${JULIA_BINDIR}/../lib"`)

+ `` is the name of your library or executable



If any step of this does not work for you, please follow the [installation guide](https://clemens-cords.com/jluna/installation.html) instead.



---



## Credits

jluna was designed and written by [Clem Cords](https://github.com/Clemapfel).



#### March 2022:


+ CMake improvements by [friendlyanon](https://github.com/friendlyanon)



## Donations



Jluna was created with no expectation of compensation and made available for free. Consider donating to reward past work and support the continued development of this library:



+ [GitHub Sponsors](https://github.com/sponsors/Clemapfel)

+ [PayPal](https://www.paypal.com/donate/?hosted_button_id=8KWF3JTDF8XL2)



---



## License & Citation



The current and all prior releases of jluna are supplied under MIT license, available [here](./LICENSE.txt).



If you would like to cite jluna in your academic publication, you can copy the entry in [CITATION.bib](CITATION.bib) to your [BibTeX](https://www.overleaf.com/learn/latex/Bibliography_management_with_bibtex) bibliography, then use the `\cite{jluna}` command anywhere in your [LaTeX](https://www.latex-project.org/) source code.



Thank you for your consideration,

C.