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#pragma once
#include "macros1.h"
#ifdef __cplusplus
// from now only C++
#include <utility>
#include <type_traits>
// before C++20
namespace cxx20_compat {
template<typename T>
struct remove_cvref {
using type = std::remove_cv_t<std::remove_reference_t<T>>;
};
} // ns cxx20_compat
template<typename t>
using remove_cvref_t = typename cxx20_compat::remove_cvref<t>::type;
template<typename t>
using to_const_ref_t = std::add_lvalue_reference_t<std::add_const_t<remove_cvref_t<t>>>;
// causes ICE in Visual Studio 2017 Preview. the ICE was reported and they handle them seriously in due time.
// the ICE is caused by decltype(auto) and const& return value
//#define eval_once(expr) ([&]() -> decltype(auto) { static decltype(auto) ret___1132 = (expr); return (decltype(ret___1132) const&) ret___1132; }())
#define eval_once(expr) eval_once2(expr, __COUNTER__)
#define eval_once2(expr, ctr) \
([&] { \
[[maybe_unused]] \
static auto PP_CAT(init, ctr) = (((void)(expr)), 0); \
}())
template<typename t>
using cv_qualified = std::conditional_t<std::is_fundamental_v<remove_cvref_t<t>>,
remove_cvref_t<t>,
to_const_ref_t<t>>;
#define progn(...) ([&]() -> decltype(auto) { __VA_ARGS__ }())
// end c++-only macros
#endif
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