82 lines
1.9 KiB
C++
82 lines
1.9 KiB
C++
// Copyright Louis Dionne 2013-2017
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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#include <boost/hana.hpp>
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#include <iostream>
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#include <string>
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#include <type_traits>
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#include <utility>
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namespace hana = boost::hana;
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using namespace std::literals;
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//! [utilities]
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template <typename Xs>
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std::string join(Xs&& xs, std::string sep) {
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return hana::fold(hana::intersperse(std::forward<Xs>(xs), sep), "", hana::_ + hana::_);
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}
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std::string quote(std::string s) { return "\"" + s + "\""; }
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template <typename T>
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auto to_json(T const& x) -> decltype(std::to_string(x)) {
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return std::to_string(x);
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}
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std::string to_json(char c) { return quote({c}); }
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std::string to_json(std::string s) { return quote(s); }
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//! [utilities]
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//! [Struct]
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template <typename T>
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std::enable_if_t<hana::Struct<T>::value,
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std::string> to_json(T const& x) {
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auto json = hana::transform(hana::keys(x), [&](auto name) {
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auto const& member = hana::at_key(x, name);
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return quote(hana::to<char const*>(name)) + " : " + to_json(member);
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});
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return "{" + join(std::move(json), ", ") + "}";
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}
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//! [Struct]
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//! [Sequence]
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template <typename Xs>
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std::enable_if_t<hana::Sequence<Xs>::value,
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std::string> to_json(Xs const& xs) {
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auto json = hana::transform(xs, [](auto const& x) {
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return to_json(x);
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});
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return "[" + join(std::move(json), ", ") + "]";
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}
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//! [Sequence]
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int main() {
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//! [usage]
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struct Car {
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BOOST_HANA_DEFINE_STRUCT(Car,
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(std::string, brand),
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(std::string, model)
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);
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};
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struct Person {
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BOOST_HANA_DEFINE_STRUCT(Person,
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(std::string, name),
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(std::string, last_name),
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(int, age)
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);
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};
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Car bmw{"BMW", "Z3"}, audi{"Audi", "A4"};
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Person john{"John", "Doe", 30};
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auto tuple = hana::make_tuple(john, audi, bmw);
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std::cout << to_json(tuple) << std::endl;
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//! [usage]
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}
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