librepr is a C++ static reflection and serialization library that provides a convenient way to generate string representations of C++ objects that can be used to reconstruct those objects. It is inspired by Python's repr function and is primarily designed to assist developers in debugging and logging.

Features

Generate string representations of C++ objects for reconstruction
Customizable formatting for user-defined types
Support for standard C++ data types and containers
Rich type and object visitation

Installation

Using submodules

Navigate to your project directory in the terminal and run the following command to add repr as a submodule:

git submodule add https://github.com/Tsche/repr external/repr

Note that the path external/repr is chosen arbitrarily. You can add the submodule at any path you like.

You may need to adjust your include path. To do so add

target_include_directories(your_target PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/external/repr/include)

to your CMakeLists.txt (replace your_target with the name of your target).

Alternatively if you do not use CMake simply pass your compiler an additional -Iexternal/repr/include (clang, gcc) or /Iexternal/repr/include (msvc) argument.

Single header

You can download a single-header distribution of repr from the URL provided:

wget https://repr.wtf/amalgamated.h -O repr.h

This command downloads the single-header file and saves it as repr.h to the current working directory. You can place this file wherever convenient (ie external/repr.h).

Compiler Explorer

Compiler Explorer supports including headers from URLs directly, hence you can simply do

//* c++ -std=c++23
#include <https://repr.wtf/amalgamated.h>
#include <print>
 
int main(){
  int foo[3] = {1, 2, 3};
  std::print("foo: {}", repr(foo));
}

Conan

‍[!IMPORTANT] repr is not yet in Conan's package repository. The following will only work if you have the package installed locally.

You can include librepr in your C++ project using the Conan package manager:

Add librepr as a dependency in your conanfile.txt:

[requires]

repr/0.1

Replace 0.1 with the desired version of librepr.
Install the dependencies using Conan:

conan install .
In your CMakeLists.txt, link against librepr:

find_package(repr REQUIRED)

target_link_libraries(your_target PRIVATE repr::repr)
Include the repr header in your C++ source files:

#include <repr>

repr

You now have added librepr as a dependency to your project using Conan.

Usage

The following example showcases usage of the repr function (or well, function object to be pedantic), which generates a reconstructible string representation of the given object. Furthermore we'll use librepr::code_for to also print the type.

//* c++ gsnapshot -std=c++23 -O3
#include <repr>
#include <print>
#include <string>
 
struct Foo {
  unsigned number;
  struct Bar {
    char c;
    float f;
  } bar;
};
 
int main() {
    auto obj = Foo{.number=42U, .bar={.c='C', .f=1.0F}};
    // dump object
    std::println("Repr: {}", repr(obj));  // Repr: Foo{.number=42U, .bar={.c='C', .f=1.0F}};
 
    // dump type
    std::println("Type:\n{}", librepr::code_for<Foo>());
 
    // showcase difference between stringification and repr
    std::println("std::format = {}   repr = {}", obj.number, repr(obj.number));
}

License

librepr is provided under the [MIT License](LICENSE). Feel free to use and modify it in your projects.

Contributing

If you'd like to contribute to librepr, please fork the repository, make your changes, and submit a pull request. We welcome any contributions, including bug fixes, new features, and improvements. Bug reports submitted as issues are also very welcome.

Contact

For questions or issues related to this library, please open an issue.

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