Standard library header <compare> (C++20)

From ja.cppreference.net

このヘッダは言語サポートライブラリの一部です。

目次 1 コンセプト 2 クラス 3 カスタマイゼーションポイントオブジェクト 4 関数 5 概要 5.1 コンセプト three_way_comparable 5.2 コンセプト three_way_comparable_with 5.3 クラス std::partial_ordering 5.4 クラス std::weak_ordering 5.5 クラス std::strong_ordering 5.6 クラス std::compare_three_way 5.7 クラス std::type_order 6 関連項目コンセプト
three_way_comparable three_way_comparable_with (C++20)	指定された型に対して演算子 <=> が一貫した結果を生成することを指定する (コンセプト)
クラス
partial_ordering (C++20)	すべての6つの演算子をサポートし、置換可能ではなく、比較不能な値を許容する3方向比較の結果型 (class)
weak_ordering (C++20)	すべての6つの演算子をサポートし、置換可能ではない3方向比較の結果型 (クラス)
strong_ordering (C++20)	すべての6つの演算子をサポートし、置換可能な3方向比較の結果型 (class)
common_comparison_category (C++20)	指定された全ての型が変換可能な最も強い比較カテゴリ (クラステンプレート)
compare_three_way_result (C++20)	指定された型に対する三方比較演算子 <=> の結果型を取得する (クラステンプレート)
compare_three_way (C++20)	x <=> y を実装する制約付き関数オブジェクト x <=> y (クラス)
カスタマイゼーションポイントオブジェクト
strong_order (C++20)	3方向比較を実行し、型 `std::strong_ordering` の結果を生成する (カスタマイゼーションポイントオブジェクト)
weak_order (C++20)	3方向比較を実行し、型 `std::weak_ordering` の結果を生成する (カスタマイゼーションポイントオブジェクト)
partial_order (C++20)	3方向比較を実行し、型 `std::partial_ordering` の結果を生成する (カスタマイゼーションポイントオブジェクト)
compare_strong_order_fallback (C++20)	3方向比較を実行し、型 `std::strong_ordering` の結果を生成する。 operator <=> が利用できない場合でも実行する (カスタマイゼーションポイントオブジェクト)
compare_weak_order_fallback (C++20)	3方向比較を実行し、結果の型を `std::weak_ordering` で生成する（ operator <=> が利用できない場合でも）（カスタマイゼーションポイントオブジェクト）
compare_partial_order_fallback (C++20)	3方向比較を実行し、たとえ `std::partial_ordering` 型の結果を生成する operator <=> が利用できない場合でも (カスタマイゼーションポイントオブジェクト)
関数
is_eq is_neq is_lt is_lteq is_gt is_gteq (C++20)	名前付き比較関数 (関数)

概要

// all freestanding
namespace std {
  // comparison category types
  class partial_ordering;
  class weak_ordering;
  class strong_ordering;

  // named comparison functions
  constexpr bool is_eq(partial_ordering cmp) noexcept { return cmp == 0; }
  constexpr bool is_neq(partial_ordering cmp) noexcept { return cmp != 0; }
  constexpr bool is_lt(partial_ordering cmp) noexcept { return cmp < 0; }
  constexpr bool is_lteq(partial_ordering cmp) noexcept { return cmp <= 0; }
  constexpr bool is_gt(partial_ordering cmp) noexcept { return cmp > 0; }
  constexpr bool is_gteq(partial_ordering cmp) noexcept { return cmp >= 0; }

  // common comparison category type
  template<class... Ts> struct common_comparison_category
  {
    using type = /* see description */;
  };
  template<class... Ts>
  using common_comparison_category_t = common_comparison_category<Ts...>::type;

  // concept three_way_comparable
  template<class T, class Cat = partial_ordering>
  concept three_way_comparable = /* see description */;
  template<class T, class U, class Cat = partial_ordering>
  concept three_way_comparable_with = /* see description */;

  // result of three-way comparison
  template<class T, class U = T> struct compare_three_way_result;

  template<class T, class U = T>
  using compare_three_way_result_t = compare_three_way_result<T, U>::type;

  // class compare_three_way
  struct compare_three_way;

  // comparison algorithms
  inline namespace /* unspecified */ {
    inline constexpr /* unspecified */ strong_order = /* unspecified */;
    inline constexpr /* unspecified */ weak_order = /* unspecified */;
    inline constexpr /* unspecified */ partial_order = /* unspecified */;
    inline constexpr /* unspecified */ compare_strong_order_fallback = /* unspecified */;
    inline constexpr /* unspecified */ compare_weak_order_fallback = /* unspecified */;
    inline constexpr /* unspecified */ compare_partial_order_fallback = /* unspecified */;
  }

  // type ordering
  template<class T, class U> struct type_order;

  template<class T, class U>
  constexpr strong_ordering type_order_v = type_order<T, U>::value;
}

コンセプト `three_way_comparable`

namespace std {
template<class T, class Cat>
concept /*compares-as*/ =            // exposition-only
  same_as<common_comparison_category_t<T, Cat>, Cat>;

template<class T, class U>
concept /*partially-ordered-with*/ = // exposition-only
  requires(const remove_reference_t<T>& t, const remove_reference_t<U>& u) {
    { t < u  } -> /*boolean-testable*/;
    { t > u  } -> /*boolean-testable*/;
    { t <= u } -> /*boolean-testable*/;
    { t >= u } -> /*boolean-testable*/;
    { u < t  } -> /*boolean-testable*/;
    { u > t  } -> /*boolean-testable*/;
    { u <= t } -> /*boolean-testable*/;
    { u >= t } -> /*boolean-testable*/;
  };

template<class T, class Cat = partial_ordering>
concept three_way_comparable =
  /*weakly-equality-comparable-with*/<T, T> && /*partially-ordered-with*/<T, T> &&
  requires(const remove_reference_t<T>& a, const remove_reference_t<T>& b) {
    { a <=> b } -> /*compares-as*/<Cat>;
  };
}

コンセプト `three_way_comparable_with`

namespace std {
template<class T, class U, class Cat = partial_ordering>
concept three_way_comparable_with =
  three_way_comparable<T, Cat> && three_way_comparable<U, Cat> &&
  /*comparison-common-type-with*/<T, U> &&
  three_way_comparable<
    common_reference_t<const remove_reference_t<T>&, const remove_reference_t<U>&>,
    Cat> &&
  /*weakly-equality-comparable-with*/<T, U> && /*partially-ordered-with*/<T, U> &&
  requires(const remove_reference_t<T>& t, const remove_reference_t<U>& u) {
    { t <=> u } -> /*compares-as*/<Cat>;
    { u <=> t } -> /*compares-as*/<Cat>;
  };
}

クラス `std::partial_ordering`

namespace std {
  class partial_ordering
  {
    int /*value*/;       // exposition-only
    bool /*is-ordered*/; // exposition-only

    // exposition-only constructors
    constexpr explicit partial_ordering(/*ord*/ v) noexcept
      : /*value*/(int(v))
      , /*is-ordered*/(true)
    {
    } // exposition-only
    constexpr explicit partial_ordering(/*ncmp*/ v) noexcept
      : /*value*/(int(v))
      , /*is-ordered*/(false)
    {
    } // exposition-only

  public:
    // valid values
    static const partial_ordering less;
    static const partial_ordering equivalent;
    static const partial_ordering greater;
    static const partial_ordering unordered;

    // comparisons
    friend constexpr bool operator==(partial_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator==(partial_ordering v,
                                     partial_ordering w) noexcept = default;
    friend constexpr bool operator<(partial_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>(partial_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<=(partial_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>=(partial_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<(/* unspecified */, partial_ordering v) noexcept;
    friend constexpr bool operator>(/* unspecified */, partial_ordering v) noexcept;
    friend constexpr bool operator<=(/* unspecified */, partial_ordering v) noexcept;
    friend constexpr bool operator>=(/* unspecified */, partial_ordering v) noexcept;
    friend constexpr partial_ordering operator<=>(partial_ordering v,
                                                  /* unspecified */) noexcept;
    friend constexpr partial_ordering operator<=>(/* unspecified */,
                                                  partial_ordering v) noexcept;
  };

  // valid values' definitions
  inline constexpr partial_ordering partial_ordering::less(/*ord*/::/*less*/);
  inline constexpr partial_ordering partial_ordering::equivalent(/*ord*/::/*equivalent*/);
  inline constexpr partial_ordering partial_ordering::greater(/*ord*/::/*greater*/);
  inline constexpr partial_ordering partial_ordering::unordered(/*ncmp*/::/*unordered*/);
}

クラス `std::weak_ordering`

namespace std {
  class weak_ordering
  {
    int /*value*/; // exposition-only

    // exposition-only constructors
    constexpr explicit weak_ordering(/*ord*/ v) noexcept
      : /*value*/(int(v))
    {
    } // exposition-only

  public:
    // valid values
    static const weak_ordering less;
    static const weak_ordering equivalent;
    static const weak_ordering greater;

    // conversions
    constexpr operator partial_ordering() const noexcept;

    // comparisons
    friend constexpr bool operator==(weak_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default;
    friend constexpr bool operator<(weak_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>(weak_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<=(weak_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>=(weak_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<(/* unspecified */, weak_ordering v) noexcept;
    friend constexpr bool operator>(/* unspecified */, weak_ordering v) noexcept;
    friend constexpr bool operator<=(/* unspecified */, weak_ordering v) noexcept;
    friend constexpr bool operator>=(/* unspecified */, weak_ordering v) noexcept;
    friend constexpr weak_ordering operator<=>(weak_ordering v,
                                               /* unspecified */) noexcept;
    friend constexpr weak_ordering operator<=>(/* unspecified */,
                                               weak_ordering v) noexcept;
  };

  // valid values' definitions
  inline constexpr weak_ordering weak_ordering::less(/*ord*/::/*less*/);
  inline constexpr weak_ordering weak_ordering::equivalent(/*ord*/::/*equivalent*/);
  inline constexpr weak_ordering weak_ordering::greater(/*ord*/::/*greater*/);
}

クラス `std::strong_ordering`

namespace std {
  class strong_ordering
  {
    int /*value*/; // exposition-only

    // exposition-only constructors
    constexpr explicit strong_ordering(/*ord*/ v) noexcept
      : /*value*/(int(v))
    {
    } // exposition-only

  public:
    // valid values
    static const strong_ordering less;
    static const strong_ordering equal;
    static const strong_ordering equivalent;
    static const strong_ordering greater;

    // conversions
    constexpr operator partial_ordering() const noexcept;
    constexpr operator weak_ordering() const noexcept;

    // comparisons
    friend constexpr bool operator==(strong_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator==(strong_ordering v,
                                     strong_ordering w) noexcept = default;
    friend constexpr bool operator<(strong_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>(strong_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<=(strong_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator>=(strong_ordering v, /* unspecified */) noexcept;
    friend constexpr bool operator<(/* unspecified */, strong_ordering v) noexcept;
    friend constexpr bool operator>(/* unspecified */, strong_ordering v) noexcept;
    friend constexpr bool operator<=(/* unspecified */, strong_ordering v) noexcept;
    friend constexpr bool operator>=(/* unspecified */, strong_ordering v) noexcept;
    friend constexpr strong_ordering operator<=>(strong_ordering v,
                                                 /* unspecified */) noexcept;
    friend constexpr strong_ordering operator<=>(/* unspecified */,
                                                 strong_ordering v) noexcept;
  };

  // valid values' definitions
  inline constexpr strong_ordering strong_ordering::less(/*ord*/::/*less*/);
  inline constexpr strong_ordering strong_ordering::equal(/*ord*/::/*equal*/);
  inline constexpr strong_ordering strong_ordering::equivalent(/*ord*/::/*equivalent*/);
  inline constexpr strong_ordering strong_ordering::greater(/*ord*/::/*greater*/);
}

クラス std:: compare_three_way

namespace std {
  struct compare_three_way {
    template<class T, class U>
    constexpr auto operator()(T&& t, U&& u) const;
    using is_transparent = /* 未指定 */;
  };
}

クラス `std::type_order`

namespace std {
  template<class T, class U> struct type_order {
    static constexpr strong_ordering value = /*TYPE-ORDER*/(T, U);
    
    using value_type = strong_ordering;
    
    constexpr operator value_type() const noexcept { return value; }
    constexpr value_type operator()() const noexcept { return value; }
  };
}

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Diagnostics library
Memory management library
Metaprogramming library (C++11)
General utilities library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Technical specifications
Symbols index
External libraries

ja.cppreference.net

Namespaces

Variants

Standard library header <compare> (C++20)

目次

コンセプト

クラス

カスタマイゼーションポイントオブジェクト

関数

概要

コンセプト `three_way_comparable`

コンセプト `three_way_comparable_with`

クラス `std::partial_ordering`

クラス `std::weak_ordering`

クラス `std::strong_ordering`

クラス std:: compare_three_way

クラス `std::type_order`

関連項目

ja.cppreference.net

Namespaces

Variants

Standard library header <compare> (C++20)

目次

コンセプト

クラス

カスタマイゼーションポイントオブジェクト

関数

概要

コンセプト three_way_comparable

コンセプト three_way_comparable_with

クラス std::partial_ordering

クラス std::weak_ordering

クラス std::strong_ordering

クラス std:: compare_three_way

クラス std::type_order

関連項目

コンセプト `three_way_comparable`

コンセプト `three_way_comparable_with`

クラス `std::partial_ordering`

クラス `std::weak_ordering`

クラス `std::strong_ordering`

クラス `std::type_order`