operator==,!=,<,<=,>,>=,<=>(std::basic_string) - cppreference.com

ヘッダ <string> で定義

2つの basic_string オブジェクトの比較

(1)

template< class CharT, class Traits, class Alloc > bool operator==( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator==( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

template< class CharT, class Traits, class Alloc > constexpr bool operator==( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++20以上)

(2)

template< class CharT, class Traits, class Alloc > bool operator!=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator!=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

(3)

template< class CharT, class Traits, class Alloc > bool operator<( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator<( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

(4)

template< class CharT, class Traits, class Alloc > bool operator>=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator>=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

(5)

template< class CharT, class Traits, class Alloc > bool operator>( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator>( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

(6)

template< class CharT, class Traits, class Alloc > bool operator>=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++14未満)

template< class CharT, class Traits, class Alloc > bool operator>=( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(C++14以上)
(C++20未満)

template< class CharT, class Traits, class Alloc > constexpr /*comp-cat*/ operator<=>( const std::basic_string<CharT,Traits,Alloc>& lhs, const std::basic_string<CharT,Traits,Alloc>& rhs ) noexcept;

(7)

(C++20以上)

basic_string オブジェクトと T のNULL終端配列の比較

(8)

template< class CharT, class Traits, class Alloc > bool operator==( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > constexpr bool operator==( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20以上)

template< class CharT, class Traits, class Alloc > bool operator==( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

(9)

template< class CharT, class Traits, class Alloc > bool operator!=( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > bool operator!=( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

(10)

template< class CharT, class Traits, class Alloc > bool operator<( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > bool operator<( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

(11)

template< class CharT, class Traits, class Alloc > bool operator<=( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > bool operator<=( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

(12)

template< class CharT, class Traits, class Alloc > bool operator>( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > bool operator>( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

(13)

template< class CharT, class Traits, class Alloc > bool operator>=( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > bool operator>=( const CharT* lhs, const std::basic_string<CharT,Traits,Alloc>& rhs );

(C++20未満)

template< class CharT, class Traits, class Alloc > constexpr /*comp-cat*/ operator<=>( const std::basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );

(14)

(C++20以上)

文字列の内容を別の文字列または CharT のヌル終端配列と比較します。

すべての比較は compare() メンバ関数を通して行われます (compare() 自身は Traits::compare() によって定義されます)。

lhs と rhs のサイズが等しく、 lhs 内のそれぞれの文字が rhs 内の同じ位置の文字と等しければ、2つの文字列は等しくなります。

順序比較は辞書的に行われます。比較は std::lexicographical_compare または std::lexicographical_compare_three_way (C++20以上) と同等な関数によって行われます。

三方比較演算子の戻り値の型 (/*comp-cat*/) は、存在すれば Traits::comparison_category、そうでなければ std::weak_ordering です。

(C++20以上)

1-7) 2つの basic_string オブジェクトを比較します。

8-14) basic_string オブジェクトと CharT のヌル終端配列を比較します。

引数

戻り値

1-6,8-13) 対応する比較が成立すれば true、そうでなければ false。

7,14) static_cast</*comp-cat*/>(lhs.compare(rhs) <=> 0)。

計算量

文字列のサイズに比例。

ノート

少なくとも1つの引数の型が std::string、 std::wstring、 std::u8string、 std::u16string または std::u32string である場合、 operator<=> の戻り値の型は std::strong_ordering です。

(C++20以上)