concepts.h

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Embedded Template Library.
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#ifndef ETL_CONCEPTS_INCLUDED
#define ETL_CONCEPTS_INCLUDED
 
#include "platform.h"
 
#include "invoke.h"
#include "type_traits.h"
#include "utility.h"
 
#if ETL_USING_CPP20
 
  #if ETL_USING_STL
    #include <concepts>
  #endif
 
namespace etl
{
 
  #if ETL_USING_STL
 
  using std::assignable_from;
  using std::common_reference_with;
  using std::common_with;
  using std::constructible_from;
  using std::convertible_to;
  using std::copy_constructible;
  using std::copyable;
  using std::default_initializable;
  using std::derived_from;
  using std::destructible;
  using std::equality_comparable;
  using std::equivalence_relation;
  using std::floating_point;
  using std::integral;
  using std::invocable;
  using std::movable;
  using std::move_constructible;
  using std::predicate;
  using std::regular;
  using std::regular_invocable;
  using std::relation;
  using std::same_as;
  using std::semiregular;
  using std::signed_integral;
  using std::strict_weak_order;
  using std::swappable;
  using std::swappable_with;
  using std::totally_ordered;
  using std::unsigned_integral;
 
  #else // not ETL_USING_STL
 
  namespace private_concepts
  {
    template <typename T, typename U>
    concept same_as_helper = etl::is_same_v<T, U>;
  }
 
  //***************************************************************************
  template <typename T, typename U>
  concept same_as = private_concepts::same_as_helper<T, U> && private_concepts::same_as_helper<U, T>;
 
  //***************************************************************************
  template <typename Derived, typename Base>
  concept derived_from = etl::is_base_of_v<Base, Derived> && etl::is_convertible_v<const volatile Derived*, const volatile Base*>;
 
  //***************************************************************************
  template <typename From, typename To>
  concept convertible_to = etl::is_convertible_v<From, To> && requires { static_cast<To>(etl::declval<From>()); };
 
  //***************************************************************************
  template < class T, typename U >
  concept common_reference_with = etl::same_as<etl::common_reference_t<T, U>, etl::common_reference_t<U, T> >
                                  && etl::convertible_to<T, etl::common_reference_t<T, U> > && etl::convertible_to<U, etl::common_reference_t<T, U> >;
 
  //***************************************************************************
  template <typename T, typename U>
  concept common_with = etl::same_as<etl::common_type_t<T, U>, etl::common_type_t<U, T> > && requires {
    static_cast<etl::common_type_t<T, U> >(etl::declval<T>());
    static_cast<etl::common_type_t<T, U> >(etl::declval<U>());
  } && etl::common_reference_with< etl::add_lvalue_reference_t<const T>, etl::add_lvalue_reference_t<const U> > && etl::common_reference_with< etl::add_lvalue_reference_t<etl::common_type_t<T, U> >, etl::common_reference_t< etl::add_lvalue_reference_t<const T>, etl::add_lvalue_reference_t<const U> > >;
 
  //***************************************************************************
  template <typename T>
  concept integral = etl::is_integral_v<T>;
 
  //***************************************************************************
  template <typename T>
  concept signed_integral = etl::integral<T> && etl::is_signed_v<T>;
 
  //***************************************************************************
  template <typename T>
  concept unsigned_integral = etl::integral<T> && !etl::signed_integral<T>;
 
  //***************************************************************************
  template <typename T>
  concept floating_point = etl::is_floating_point_v<T>;
 
  //***************************************************************************
  template <typename LHS, typename RHS>
  concept assignable_from =
    etl::is_lvalue_reference_v<LHS> && etl::common_reference_with< const etl::remove_reference_t<LHS>&, const etl::remove_reference_t<RHS>&>
    && requires(LHS lhs, RHS&& rhs) {
         { lhs = etl::forward<RHS>(rhs) } -> etl::same_as<LHS>;
       };
 
  //***************************************************************************
  template <typename F, typename... Args>
  concept invocable = etl::is_invocable_v<F, Args...>;
 
  //***************************************************************************
  template <typename F, typename... Args>
  concept regular_invocable = etl::invocable<F, Args...>;
 
  //***************************************************************************
  template <typename T>
  concept destructible = requires(T& t) {
    { t.~T() } noexcept;
  };
 
  //***************************************************************************
  template <typename T, typename... Args>
  concept constructible_from = etl::destructible<T> && etl::is_constructible_v<T, Args...>;
 
  //***************************************************************************
  template <typename T>
  concept default_initializable = etl::constructible_from<T> && requires {
    T{};
    ::new T;
  };
 
  //***************************************************************************
  template <typename T>
  concept move_constructible = etl::constructible_from<T, T> && etl::convertible_to<T, T>;
 
  //***************************************************************************
  template <typename T>
  concept copy_constructible =
    etl::move_constructible<T> && etl::constructible_from<T, T&> && etl::convertible_to<T&, T> && etl::constructible_from<T, const T&>
    && etl::convertible_to<const T&, T> && etl::constructible_from<T, const T> && etl::convertible_to<const T, T>;
 
  //***************************************************************************
  namespace private_concepts
  {
    template <typename T>
    concept boolean_testable = etl::convertible_to<T, bool> && requires(T&& t) {
      { !etl::forward<T>(t) } -> etl::convertible_to<bool>;
    };
  } // namespace private_concepts
 
  //***************************************************************************
  template <typename T>
  concept equality_comparable = requires(const etl::remove_reference_t<T>& a, const etl::remove_reference_t<T>& b) {
    { a == b } -> private_concepts::boolean_testable;
    { a != b } -> private_concepts::boolean_testable;
  };
 
  //***************************************************************************
  template <typename T>
  concept totally_ordered = etl::equality_comparable<T> && requires(const etl::remove_reference_t<T>& a, const etl::remove_reference_t<T>& b) {
    { a < b } -> private_concepts::boolean_testable;
    { a > b } -> private_concepts::boolean_testable;
    { a <= b } -> private_concepts::boolean_testable;
    { a >= b } -> private_concepts::boolean_testable;
  };
 
  //***************************************************************************
  template <typename T>
  concept swappable = requires(T& a, T& b) { etl::swap(a, b); };
 
  //***************************************************************************
  template <typename T, typename U>
  concept swappable_with = etl::common_reference_with<etl::remove_reference_t<T>&, etl::remove_reference_t<U>&> && requires(T&& t, U&& u) {
    etl::swap(etl::forward<T>(t), etl::forward<T>(t));
    etl::swap(etl::forward<U>(u), etl::forward<U>(u));
    etl::swap(etl::forward<T>(t), etl::forward<U>(u));
    etl::swap(etl::forward<U>(u), etl::forward<T>(t));
  };
 
  //***************************************************************************
  template <typename T>
  concept movable = etl::is_object_v<T> && etl::move_constructible<T> && etl::assignable_from<T&, T> && etl::swappable<T>;
 
  //***************************************************************************
  template <typename T>
  concept copyable = etl::copy_constructible<T> && etl::movable<T> && etl::assignable_from<T&, T&> && etl::assignable_from<T&, const T&>
                     && etl::assignable_from<T&, const T>;
 
  //***************************************************************************
  template <typename T>
  concept semiregular = etl::copyable<T> && etl::default_initializable<T>;
 
  //***************************************************************************
  template <typename T>
  concept regular = etl::semiregular<T> && etl::equality_comparable<T>;
 
  //***************************************************************************
  template <typename F, typename... Args>
  concept predicate = etl::regular_invocable<F, Args...> && private_concepts::boolean_testable<etl::invoke_result_t<F, Args...> >;
 
  //***************************************************************************
  template <typename R, typename T, typename U>
  concept relation = etl::predicate<R, T, T> && etl::predicate<R, U, U> && etl::predicate<R, T, U> && etl::predicate<R, U, T>;
 
  //***************************************************************************
  template <typename R, typename T, typename U>
  concept equivalence_relation = etl::relation<R, T, U>;
 
  //***************************************************************************
  template <typename R, typename T, typename U>
  concept strict_weak_order = etl::relation<R, T, U>;
 
  #endif
} // namespace etl
#endif
#endif