ceph/src/boost/libs/pfr/README.md

   1 # Boost.PFR
   2
   3 This is a C++14 library for very basic reflection that gives you access to structure elements by index and provides other `std::tuple` like methods for user defined types without any macro or boilerplate code.
   4
   5
   6 [Latest documentation](http://apolukhin.github.com/magic_get/index.html)
   7
   8 ### Test results
   9
  10 Branches        | Build         | Tests coverage | More info
  11 ----------------|-------------- | -------------- |-----------
  12 Develop:        | [![Build Status](https://travis-ci.org/apolukhin/magic_get.svg?branch=develop)](https://travis-ci.org/apolukhin/magic_get) [![Build status](https://ci.appveyor.com/api/projects/status/3tled9gd24k9paia/branch/develop?svg=true)](https://ci.appveyor.com/project/apolukhin/magic-get/branch/develop) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=develop)](https://coveralls.io/github/apolukhin/magic_get?branch=develop) | [details...](http://www.boost.org/development/tests/develop/developer/pfr.html)
  13 Master:         | [![Build Status](https://travis-ci.org/apolukhin/magic_get.svg?branch=master)](https://travis-ci.org/apolukhin/magic_get) [![Build status](https://ci.appveyor.com/api/projects/status/3tled9gd24k9paia/branch/master?svg=true)](https://ci.appveyor.com/project/apolukhin/magic-get/branch/master) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=master)](https://coveralls.io/github/apolukhin/magic_get?branch=master) | [details...](http://www.boost.org/development/tests/master/developer/pfr.html)
  14
  15 ### Motivating Example #0
  16 ```c++
  17 #include <iostream>
  18 #include <fstream>
  19 #include <string>
  20
  21 #include "boost/pfr.hpp"
  22
  23 struct some_person {
  24   std::string name;
  25   unsigned birth_year;
  26 };
  27
  28 int main(int argc, const char* argv[]) {
  29   some_person val{"Edgar Allan Poe", 1809};
  30
  31   std::cout << boost::pfr::get<0>(val)                // No macro!
  32       << " was born in " << boost::pfr::get<1>(val);  // Works with any aggregate initializables!
  33
  34   if (argc > 1) {
  35     std::ofstream ofs(argv[1]);
  36     ofs << boost::pfr::io(val);                       // File now contains: {"Edgar Allan Poe", 1809}
  37   }
  38 }
  39 ```
  40 Outputs:
  41 ```
  42 Edgar Allan Poe was born in 1809
  43 ```
  44
  45
  46 ### Motivating Example #1
  47 ```c++
  48 #include <iostream>
  49 #include "boost/pfr/precise.hpp"
  50
  51 struct my_struct { // no ostream operator defined!
  52     int i;
  53     char c;
  54     double d;
  55 };
  56
  57 int main() {
  58     my_struct s{100, 'H', 3.141593};
  59     std::cout << "my_struct has " << boost::pfr::tuple_size<my_struct>::value
  60         << " fields: " << boost::pfr::io(s) << "\n";
  61 }
  62
  63 ```
  64
  65 Outputs:
  66 ```
  67 my_struct has 3 fields: {100, H, 3.14159}
  68 ```
  69
  70 ### Motivating Example #2
  71
  72 ```c++
  73 #include <iostream>
  74 #include "boost/pfr/precise.hpp"
  75
  76 struct my_struct { // no ostream operator defined!
  77     std::string s;
  78     int i;
  79 };
  80
  81 int main() {
  82     my_struct s{{"Das ist fantastisch!"}, 100};
  83     std::cout << "my_struct has " << boost::pfr::tuple_size<my_struct>::value
  84         << " fields: " << boost::pfr::io(s) << "\n";
  85 }
  86
  87 ```
  88
  89 Outputs:
  90 ```
  91 my_struct has 2 fields: {"Das ist fantastisch!", 100}
  92 ```
  93
  94
  95 ### Requirements and Limitations
  96
  97 [See docs](http://apolukhin.github.com/magic_get/index.html).
  98
  99 ### License
 100
 101 Distributed under the [Boost Software License, Version 1.0](http://boost.org/LICENSE_1_0.txt).