pfr/example/quick_examples.cpp

// Copyright 2016-2020 Antony Polukhin

// Distributed under the Boost Software License, Version 1.0.
// (See the accompanying file LICENSE_1_0.txt
// or a copy at <http://www.boost.org/LICENSE_1_0.txt>.)

#include <cassert>
#include <iostream>
#include <unordered_set>
#include <set>

#include <boost/pfr.hpp>
#include <boost/type_index.hpp>


//[pfr_quick_examples_structures
struct foo {
    int integer;
    double real;
    
    void operator +=(int v) {
        integer += v * 10;
        real += v * 100;
    }
};

struct bar {
    char character;
    foo f;
};

bar var{'A', {777, 3.141593}};
//]
    
inline std::ostream& operator<<(std::ostream& os, const bar& b) {
    return os << '{' << b.character << ", {" << b.f.integer << ", " << b.f.real << "}}";
}

void test_examples() {

#if BOOST_PFR_USE_CPP17
  {
//[pfr_quick_examples_ops
    struct test { std::string f1; std::string_view f2; };
    using namespace boost::pfr::ops; // Defines comparisons
    assert((test{"abc", ""} > test{"aaa", "zomg"}));
//]
  }
#endif
    
  {  
    bar var{'A', {777, 3.141593}};
    
//[pfr_quick_examples_for_each    
    // increments first field on 1, calls foo::operator+= for second field
    boost::pfr::for_each_field(var, [](auto& field) {
        field += 1;
    });
//]
    
    std::cout << "flat_for_each_field outputs:\n" << var << '\n';
  }
    
  {
    bar var{'A', {777, 3.141593}};

//[pfr_quick_examples_for_each_idx  
    boost::pfr::for_each_field(var, [](auto& field, std::size_t idx) {
        std::cout << idx << ": "
            << boost::typeindex::type_id_runtime(field) << '\n';
    });
//]
  }


  {
//[pfr_quick_examples_tuple_size
    std::cout << "tuple_size: "
        << boost::pfr::tuple_size<bar>::value << '\n';
//]
  }

#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
  {
    bar var{'A', {777, 3.141593}};
//[pfr_quick_examples_get_1
    boost::pfr::get<1>(var) = foo{1, 2}; // C++17 or Loophole is required
//]
    std::cout << "boost::pfr::get<1>(var) outputs:\n" << var << '\n';
  }
#endif
  
  {
    bar var{'A', {777, 3.141593}};
//[pfr_quick_examples_get_2
    boost::pfr::get<1>(var.f) = 42.01;
//]
    std::cout << "boost::pfr::get<1>(var.f) outputs:\n" << var << '\n';
  }

#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
  {
    bar var{'A', {777, 3.141593}};
//[pfr_quick_examples_structure_to_tuple
    // C++17 or Loophole is required
    std::tuple<char, foo> t = boost::pfr::structure_to_tuple(var);
    std::get<1>(t) = foo{1, 2};
//]
    std::cout << "boost::pfr::structure_to_tuple(var) :\n" << var << '\n';
  }
#endif

#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
  {
    bar var{'A', {777, 3.141593}};
//[pfr_quick_examples_structure_tie
    // C++17 or Loophole is required
    std::tuple<char&, foo&> t = boost::pfr::structure_tie(var);
    std::get<1>(t) = foo{1, 2};
//]
    std::cout << "boost::pfr::structure_tie(var) :\n" << var << '\n';
  }
#endif

} // void test_examples() {


int main() {
    test_examples();
}