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标准库头文件 <concepts>

此头文件是概念库的一部分。

概念

核心语言概念
(C++20)
 指定一个类型与另一类型相同
(概念)
(C++20)
 指定一个类型派生自另一类型
(概念)
(C++20)
 指定一个类型能隐式转换成另一类型
(概念)
(C++20)
 指定两个类型共有一个公共引用类型
(概念)
(C++20)
 指定两个类型共有一个公共类型
(概念)
(C++20)
 指定类型为整型类型
(概念)
(C++20)
 指定类型为有符号的整型类型
(概念)
(C++20)
 指定类型为无符号的整型类型
(概念)
(C++20)
 指定类型为浮点类型
(概念)
(C++20)
 指定一个类型能从另一类型赋值
(概念)
(C++20)
 指定一个类型能进行交换，或两个类型能彼此交换
(概念)
(C++20)
 指定能销毁该类型的对象
(概念)
(C++20)
 指定该类型的变量能从一组实参类型进行构造，或绑定到一组实参类型
(概念)
(C++20)
 指定能默认构造一个类型的对象
(概念)
(C++20)
 指定能移动构造一个类型的对象
(概念)
(C++20)
 指定能复制构造和移动构造一个类型的对象
(概念)
比较概念
(C++20)
 指定类型能用于布尔语境
(概念)
(C++20)
 指定运算符 == 为等价关系
(概念)
(C++20)
 指定比较运算符在该类型上产生全序
(概念)
对象概念
(C++20)
 指定能移动及交换一个类型的对象
(概念)
(C++20)
 指定能复制、移动及交换一个类型的对象
(概念)
(C++20)
 指定能赋值、移动、交换及默认构造一个类型的对象
(概念)
(C++20)
 指定类型为正则，即它既为 semiregular 亦为 equality_comparable
(概念)
可调用概念
(C++20)
 指定能以给定的一组实参类型调用的可调用类型
(概念)
(C++20)
 指定可调用类型为布尔谓词
(概念)
(C++20)
 指定可调用类型为二元关系
(概念)
(C++20)
 指定 relation 施加等价关系
(概念)
(C++20)
 指定一个 relation 所强加的是严格弱序
(概念)

定制点对象

(C++20)
 交换两个对象的值
(定制点对象)


概要

namespace std {
  // 语言相关概念
  // 概念 same_as
  template<class T, class U>
    concept same_as = /* 见描述 */;
 
  // 概念 derived_from
  template<class Derived, class Base>
    concept derived_from = /* 见描述 */;
 
  // 概念 convertible_to
  template<class From, class To>
    concept convertible_to = /* 见描述 */;
 
  // 概念 common_reference_with
  template<class T, class U>
    concept common_reference_with = /* 见描述 */;
 
  // 概念 common_with
  template<class T, class U>
    concept common_with = /* 见描述 */;
 
  // 算术概念
  template<class T>
    concept integral = /* 见描述 */;
  template<class T>
    concept signed_integral = /* 见描述 */;
  template<class T>
    concept unsigned_integral = /* 见描述 */;
  template<class T>
    concept floating_point = /* 见描述 */;
 
  // 概念 assignable_from
  template<class LHS, class RHS>
    concept assignable_from = /* 见描述 */;
 
  // 概念 swappable
  namespace ranges {
    inline namespace /* 未指明 */ {
      inline constexpr /* 未指明 */ swap = /* 未指明 */;
    }
  }
  template<class T>
    concept swappable = /* 见描述 */;
  template<class T, class U>
    concept swappable_with = /* 见描述 */;
 
  // 概念 destructible
  template<class T>
    concept destructible = /* 见描述 */;
 
  // 概念 constructible_from
  template<class T, class... Args>
    concept constructible_from = /* 见描述 */;
 
  // 概念 default_initializable
  template<class T>
    concept default_initializable = /* 见描述 */;
 
  // 概念 move_constructible
  template<class T>
    concept move_constructible = /* 见描述 */;
 
  // 概念 copy_constructible
  template<class T>
    concept copy_constructible = /* 见描述 */;
 
  // 比较概念
  // 概念 boolean
  template<class B>
    concept boolean = /* 见描述 */;
 
  // 概念 equality_comparable
  template<class T>
    concept equality_comparable = /* 见描述 */;
  template<class T, class U>
    concept equality_comparable_with = /* 见描述 */;
 
  // 概念 totally_ordered
  template<class T>
    concept totally_ordered = /* 见描述 */;
  template<class T, class U>
    concept totally_ordered_with = /* 见描述 */;
 
  // 对象概念
  template<class T>
    concept movable = /* 见描述 */;
  template<class T>
    concept copyable = /* 见描述 */;
  template<class T>
    concept semiregular = /* 见描述 */;
  template<class T>
    concept regular = /* 见描述 */;
 
  // 可调用概念
  // 概念 invocable
  template<class F, class... Args>
    concept invocable = /* 见描述 */;
 
  // 概念 regular_invocable
  template<class F, class... Args>
    concept regular_invocable = /* 见描述 */;
 
  // 概念 predicate
  template<class F, class... Args>
    concept predicate = /* 见描述 */;
 
  // 概念 relation
  template<class R, class T, class U>
    concept relation = /* 见描述 */;
 
  // 概念 equivalence_relation
  template<class R, class T, class U>
    concept equivalence_relation = /* 见描述 */;
 
  // 概念 strict_weak_order
  template<class R, class T, class U>
    concept strict_weak_order = /* 见描述 */;
}

概念 same_as

template<class T, class U>
  concept __SameImpl = is_same_v<T, U>;  // 仅为阐释
 
template<class T, class U>
  concept same_as = __SameImpl<T, U> && __SameImpl<U, T>;

概念 derived_from

template<class Derived, class Base>
  concept derived_from =
    is_base_of_v<Base, Derived> &&
    is_convertible_v<const volatile Derived*, const volatile Base*>;

概念 convertible_to

template<class From, class To>
  concept convertible_to =
    is_convertible_v<From, To> &&
    requires(From (&f)()) {
      static_cast<To>(f());
    };

概念 common_reference_with

template<class T, class U>
  concept common_reference_with =
    same_as<common_reference_t<T, U>, common_reference_t<U, T>> &&
    convertible_to<T, common_reference_t<T, U>> &&
    convertible_to<U, common_reference_t<T, U>>;

概念 common_with

template<class T, class U>
  concept common_with =
    same_as<common_type_t<T, U>, common_type_t<U, T>> &&
    requires {
      static_cast<common_type_t<T, U>>(declval<T>());
      static_cast<common_type_t<T, U>>(declval<U>());
    } &&
    common_reference_with<
      add_lvalue_reference_t<const T>,
      add_lvalue_reference_t<const U>> &&
    common_reference_with<
      add_lvalue_reference_t<common_type_t<T, U>>,
      common_reference_t<
        add_lvalue_reference_t<const T>,
        add_lvalue_reference_t<const U>>>;

概念 integral

template<class T>
  concept integral = is_integral_v<T>;

概念 signed_integral

template<class T>
  concept signed_integral = integral<T> && is_signed_v<T>;

概念 unsigned_integral

template<class T>
  concept unsigned_integral = integral<T> && !signed_integral<T>;

概念 floating_point

template<class T>
  concept floating_point = is_floating_point_v<T>;

概念 assignable_from

template<class LHS, class RHS>
  concept assignable_from =
    is_lvalue_reference_v<LHS> &&
    common_reference_with<
      const remove_reference_t<LHS>&,
      const remove_reference_t<RHS>&> &&
    requires(LHS lhs, RHS&& rhs) {
      { lhs = std::forward<RHS>(rhs) } -> same_as<LHS>;

概念 swappable

template<class T>
  concept swappable = requires(T& a, T& b) { ranges::swap(a, b); };

概念 swappable_with

template<class T, class U>
  concept swappable_with =
    common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&> &&
    requires(T&& t, U&& u) {
      ranges::swap(std::forward<T>(t), std::forward<T>(t));
      ranges::swap(std::forward<U>(u), std::forward<U>(u));
      ranges::swap(std::forward<T>(t), std::forward<U>(u));
      ranges::swap(std::forward<U>(u), std::forward<T>(t));
    };

概念 destructible

template<class T>
  concept destructible = is_nothrow_destructible_v<T>;

概念 constructible_from

template<class T, class... Args>
  concept constructible_from = destructible<T> && is_constructible_v<T, Args...>;

概念 default_initializable

template<class T>
  inline constexpr bool __is_default_initializable = /* 见定义 */;  // 仅用于阐释
 
template<class T>
  concept default_initializable = constructible_from<T> &&
                                  requires{ T{}; } &&
                                  __is_default_initializable<T>;

概念 move_constructible

template<class T>
  concept move_constructible = constructible_from<T, T> && convertible_to<T, T>;

概念 copy_constructible

template<class T>
  concept copy_constructible =
    move_constructible<T> &&
    constructible_from<T, T&> && convertible_to<T&, T> &&
    constructible_from<T, const T&> && convertible_to<const T&, T> &&
    constructible_from<T, const T> && convertible_to<const T, T>;

概念 boolean

template<class B>
  concept boolean =
    movable<remove_cvref_t<B>> &&
    requires(const remove_reference_t<B>& b1,
             const remove_reference_t<B>& b2, const bool a) {
      { b1 } -> convertible_to<bool>;
      { !b1 } -> convertible_to<bool>;
      { b1 && b2 } -> same_as<bool>;
      { b1 &&  a } -> same_as<bool>;
      {  a && b2 } -> same_as<bool>;
      { b1 || b2 } -> same_as<bool>;
      { b1 ||  a } -> same_as<bool>;
      {  a || b2 } -> same_as<bool>;
      { b1 == b2 } -> convertible_to<bool>;
      { b1 ==  a } -> convertible_to<bool>;
      {  a == b2 } -> convertible_to<bool>;
      { b1 != b2 } -> convertible_to<bool>;
      { b1 !=  a } -> convertible_to<bool>;
      {  a != b2 } -> convertible_to<bool>;
    };

概念 equality_comparable

template<class T, class U>
  concept __WeaklyEqualityComparableWith = // 仅为阐释
    requires(const remove_reference_t<T>& t,
             const remove_reference_t<U>& u) {
      { t == u } -> boolean;
      { t != u } -> boolean;
      { u == t } -> boolean;
      { u != t } -> boolean;
    };
 
template<class T>
  concept equality_comparable = __WeaklyEqualityComparableWith<T, T>;

概念 equality_comparable_with

template<class T, class U>
  concept equality_comparable_with =
    equality_comparable<T> && equality_comparable<U> &&
    common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&> &&
    equality_comparable<
      common_reference_t<
        const remove_reference_t<T>&,
        const remove_reference_t<U>&>> &&
    __WeaklyEqualityComparableWith<T, U>;

概念 totally_ordered

template<class T>
  concept totally_ordered =
    equality_comparable<T> &&
    requires(const remove_reference_t<T>& a,
             const remove_reference_t<T>& b) {
      { a <  b } -> boolean;
      { a >  b } -> boolean;
      { a <= b } -> boolean;
      { a >= b } -> boolean;
    };

概念 totally_ordered_with

template<class T, class U>
  concept totally_ordered_with =
    totally_ordered<T> && totally_ordered<U> &&
    common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&> &&
    totally_ordered<
      common_reference_t<
        const remove_reference_t<T>&,
        const remove_reference_t<U>&>> &&
    equality_comparable_with<T, U> &&
    requires(const remove_reference_t<T>& t,
             const remove_reference_t<U>& u) {
      { t <  u } -> boolean;
      { t >  u } -> boolean;
      { t <= u } -> boolean;
      { t >= u } -> boolean;
      { u <  t } -> boolean;
      { u >  t } -> boolean;
      { u <= t } -> boolean;
      { u >= t } -> boolean;
    };

概念 movable

template<class T>
  concept movable = is_object_v<T> && move_constructible<T> &&
                    assignable_from<T&, T> && swappable<T>;

概念 copyable

template<class T>
  concept copyable = copy_constructible<T> && movable<T> && assignable_from<T&, const T&>;

概念 semiregular

template<class T>
  concept semiregular = copyable<T> && default_initializable<T>;

概念 regular

template<class T>
  concept regular = semiregular<T> && equality_comparable<T>;

概念 invocable

template<class F, class... Args>
  concept invocable = requires(F&& f, Args&&... args) {
    invoke(std::forward<F>(f), std::forward<Args>(args)...);
      // 不要求保持相等性
  };

概念 regular_invocable

template<class F, class... Args>
  concept regular_invocable = invocable<F, Args...>;

概念 predicate

template<class F, class... Args>
  concept predicate =
    regular_invocable<F, Args...> && boolean<invoke_result_t<F, Args...>>;

概念 relation

template<class R, class T, class U>
  concept relation =
    predicate<R, T, T> && predicate<R, U, U> &&
    predicate<R, T, U> && predicate<R, U, T>;

概念 equivalence_relation

template<class R, class T, class U>
  concept equivalence_relation = relation<R, T, U>;

概念 strict_weak_order

template<class R, class T, class U>
  concept strict_weak_order = relation<R, T, U>;