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Aggreget

Description

Aggreget (aggreget get) let you use your structures like tuples. Similar to MagicGet but using C++ 20 concepts.

Your structure must be an aggregate type and all its fields must be default constructible.

Requires C++20. (because of concepts)

Tested with gcc 10 20191220 (experimental).

You can try it online on: https://godbolt.org/z/sW7zA8.

Examples

Imagine you have the following structure:

struct AwesomeStruct
{
	std::string str;
	int a;
	double trololol;
};

AwesomeStruct my_awesome_struct = {"Yolol", 42, 42.42};

You can transform it into a tuple and use your tuple:

std::cout << "To tuple then std::get" << std::endl;
auto my_struct_as_tuple = aggreget::to_tuple(my_awesome_struct);
std::cout << "The string is: " << std::get<0>(my_struct_as_tuple) << std::endl;
std::cout << "The int is: " << std::get<1>(my_struct_as_tuple) << std::endl;
std::cout << "The double is: " << std::get<2>(my_struct_as_tuple) << std::endl;

You can even get directly a a field with aggreget::get:

std::cout << "Aggreget (The same as above but in one function)" << std::endl;
std::cout << "The string is: " << aggreget::get<0>(my_awesome_struct) << std::endl;
std::cout << "The int is: " << aggreget::get<1>(my_awesome_struct) << std::endl;
std::cout << "The double is: " << aggreget::get<2>(my_awesome_struct) << std::endl;

The whole example is in the file example.cpp.

How to add it into my project?

Just add the files aggreget.hpp, aggregate_concept.hpp and aggreget_generated.hpp into your project include path.

How does it work?

There is a concept for each number of attributes a structure can have (default is 0 to 24). To declare these concepts I use aggregate initialization: if I can initialize a structure like this MyStruct { {}, {}} this mean that the structure has atleast 2 fields. Then I use the fact that concept are use in overload resolution, so there is an overload of to_tuple function for each concept. To transform the structure into a tuple I use structure binding.

TODO

  • A Better (and updated) readme (Explanations, example, how to use the python, etc)
  • Implement stuff with "tuple_size"
  • Better unit tests
  • Use feature test macro
  • Add a way to detect if a structure has too many fields and make a static assertion to say that you need to generate the aggreget_generated.hpp file with more fields
  • Port it on vcpkg ?
  • ???
  • Profit