logical.hpp

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#ifndef SHARE_METAPROGRAMMING_LOGICAL_HPP
#define SHARE_METAPROGRAMMING_LOGICAL_HPP

// Stand-ins for C++17 logical operations on types.

#include <type_traits>

// Stand-in for C++17 std::bool_constant<value>.
template<bool Value>
using BoolConstant = std::integral_constant<bool, Value>;

// Stand-in for C++17 std::conjunction<T...>
template<typename... T>
struct Conjunction : public std::true_type {};

template<typename T1>
struct Conjunction<T1> : public T1 {};

template<typename T1, typename... T>
struct Conjunction<T1, T...> :
  public std::conditional_t<bool(T1::value), Conjunction<T...>, T1>
{};

// Stand-in for C++17 std::disjunction<T...>.
template<typename... T>
struct Disjunction : public std::false_type {};

template<typename T1>
struct Disjunction<T1> : public T1 {};

template<typename T1, typename... T>
struct Disjunction<T1, T...> :
  public std::conditional_t<bool(T1::value), T1, Disjunction<T...>>
{};

// Stand-in for C++17 std::negation<T>.
template<typename T>
using Negation = BoolConstant<!bool(T::value)>;

#endif // SHARE_METAPROGRAMMING_LOGICAL_HPP