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#pragma once
#include <climits>
#include <functional>
#include <type_traits>
namespace OpenVic::utility {
[[noreturn]] inline void unreachable() {
// Uses compiler specific extensions if possible.
// Even if no extension is used, undefined behavior is still raised by
// an empty function body and the noreturn attribute.
#ifdef __GNUC__ // GCC, Clang, ICC
__builtin_unreachable();
#elif defined(_MSC_VER) // MSVC
__assume(false);
#endif
}
template<class T>
constexpr inline void hash_combine(std::size_t& s, const T& v) {
std::hash<T> h;
s ^= h(v) + 0x9e3779b9 + (s << 6) + (s >> 2);
}
template<size_t Shift, class T>
constexpr inline void hash_combine_index(std::size_t& s, const T& v) {
std::hash<T> h;
if constexpr(Shift == 0) {
s = h(v);
} else {
s ^= h(v) << Shift;
}
}
template<class T, typename ...Args>
constexpr void perfect_hash(std::size_t& s, T&& v, Args&&... args) {
static_assert(sizeof(T) + (sizeof(Args) + ...) <= sizeof(std::size_t), "Perfect hashes must be able to fit into size_t");
std::hash<T> h;
if constexpr(sizeof...(args) == 0) {
s = h(v);
} else {
const std::tuple arg_tuple { args... };
s = h(v) << (sizeof(T) * CHAR_BIT);
([&]{
// If args is not last pointer of args
if (static_cast<const void*>(&(std::get<sizeof...(args) - 1>(arg_tuple))) != static_cast<const void*>(&args)) {
s <<= sizeof(Args) * CHAR_BIT;
}
s |= std::hash<Args>{}(args);
}(), ...);
}
}
template<typename T, template<typename...> class Z>
struct is_specialization_of : std::false_type {};
template<typename... Args, template<typename...> class Z>
struct is_specialization_of<Z<Args...>, Z> : std::true_type {};
template<typename T, template<typename...> class Z>
inline constexpr bool is_specialization_of_v = is_specialization_of<T, Z>::value;
}
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