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62 lines
1.8 KiB
62 lines
1.8 KiB
3 years ago
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#pragma once
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#include <type_traits>
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#include <nlohmann/detail/meta/void_t.hpp>
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// https://en.cppreference.com/w/cpp/experimental/is_detected
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namespace nlohmann
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{
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namespace detail
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{
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struct nonesuch
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{
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nonesuch() = delete;
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~nonesuch() = delete;
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nonesuch(nonesuch const&) = delete;
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nonesuch(nonesuch const&&) = delete;
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void operator=(nonesuch const&) = delete;
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void operator=(nonesuch&&) = delete;
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};
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template<class Default,
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class AlwaysVoid,
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template<class...> class Op,
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class... Args>
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struct detector
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{
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using value_t = std::false_type;
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using type = Default;
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};
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template<class Default, template<class...> class Op, class... Args>
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struct detector<Default, void_t<Op<Args...>>, Op, Args...>
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{
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using value_t = std::true_type;
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using type = Op<Args...>;
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};
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template<template<class...> class Op, class... Args>
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using is_detected = typename detector<nonesuch, void, Op, Args...>::value_t;
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template<template<class...> class Op, class... Args>
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struct is_detected_lazy : is_detected<Op, Args...> { };
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template<template<class...> class Op, class... Args>
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using detected_t = typename detector<nonesuch, void, Op, Args...>::type;
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template<class Default, template<class...> class Op, class... Args>
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using detected_or = detector<Default, void, Op, Args...>;
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template<class Default, template<class...> class Op, class... Args>
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using detected_or_t = typename detected_or<Default, Op, Args...>::type;
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template<class Expected, template<class...> class Op, class... Args>
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using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
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template<class To, template<class...> class Op, class... Args>
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using is_detected_convertible =
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std::is_convertible<detected_t<Op, Args...>, To>;
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} // namespace detail
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} // namespace nlohmann
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