Named: Compile-Time Named Access to Structured Data in C++

A C++20 header-only library for working with tuples, arrays, and bitsets using compile-time string tags.

Overview

Named provides C++ types for named access to structured data, using string literals at compile time.
It includes:

• NamedTuple: a tuple with name-based accessors
• TaggedArray: a fixed-size array with named elements
• TaggedBitset: a fixed-size bitset with named bits

Requirements

• C++20 compliant compiler
• No external dependencies
• Include the Named/ directory in your project

Single Include

There is a single include version at single_include/Named.hpp

I will attempt to keep the single include updated with the rest of the code, however, it is annoying so do not rely on this.

Quick Start

NamedTuple

#include <Named/NamedTuple.hpp>
#include <iostream>

namespace named = mguid;

int main() {
  named::NamedTuple<
    named::NamedType<"x", int>,
    named::NamedType<"y", int>
  > point;

  point.get<"x">() = 3;
  point.get<"y">() = 4;

  std::cout << "Point: (" << point.get<"x">() << ", " << point.get<"y">() << ")\n";
}

Tagged Initialization with User-Defined Literals

#include <Named/NamedTuple.hpp>
#include <iostream>

namespace named = mguid;
using namespace mguid::literals;

int main() {
  named::NamedTuple coord{
    "lat"_named = 42.0,
    "lon"_named = -71.0
  };

  std::cout << "Latitude: " << coord.get<"lat">()
            << ", Longitude: " << coord.get<"lon">() << "\n";
}

Tagged Array

#include <Named/TaggedArray.hpp>
#include <iostream>

namespace named = mguid;

int main() {
  named::TaggedArray<float, "width", "height"> dims{1024.0f, 768.0f};

  dims.set<"height">(800.0f);

  std::cout << "Width: " << dims.get<"width">()
            << ", Height: " << dims.get<"height">() << "\n";
}

TaggedBitset

#include <Named/TaggedBitset.hpp>
#include <iostream>

namespace named = mguid;

int main() {
  named::TaggedBitset<"visible", "enabled"> flags;

  flags.set<"visible">();
  flags.set<"enabled">();

  std::cout << std::boolalpha;
  std::cout << "Visible: " << flags.test<"visible">() << "\n";
  std::cout << "Enabled: " << flags.test<"enabled">() << "\n";
}

Additional Utilities

make_tuple

#include <Named/NamedTuple.hpp>

namespace named = mguid;

int main() {
  auto color = named::make_tuple(
    named::NamedTypeV<"r">(255),
    named::NamedTypeV<"g">(128),
    named::NamedTypeV<"b">(64)
  );

  int green = color.get<"g">();
}

tuple_cat

#include <Named/NamedTuple.hpp>
#include <iostream>

namespace named = mguid;

int main() {
  auto a = named::make_tuple(mguid::NamedTypeV<"x">(1));
  auto b = named::make_tuple(mguid::NamedTypeV<"y">(2));

  auto result = named::tuple_cat(a, b);

  std::cout << result.get<"x">() << ", " << result.get<"y">() << "\n";
}

Compile-Time Diagnostics

If you use an invalid tag such as:

tuple.get<"z">();

If you are using GCC or Clang a message will be somewhere in the compiler error telling you the closest key to the one provided:

"z" was not found in ["x", "y"]. Did you mean "y"?

This is a sort of misuse of the type system.

Unfortunately, there is no way to static assert and show a compile time generated message yet.

License

This project is licensed under the MIT License.