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operator==,!=,<,<=,>,>=,<=>(std::basic_string_view)

From cppreference.com
 
 
 
 
Defined in header <string_view>
template< class CharT, class Traits >

constexpr bool operator==( std::basic_string_view<CharT,Traits> lhs,

                           std::basic_string_view<CharT,Traits> rhs ) noexcept;
(1) (since C++17)
template< class CharT, class Traits >

constexpr bool operator!=( std::basic_string_view<CharT,Traits> lhs,

                           std::basic_string_view<CharT,Traits> rhs ) noexcept;
(2) (since C++17)
(until C++20)
template< class CharT, class Traits >

constexpr bool operator<( std::basic_string_view<CharT,Traits> lhs,

                          std::basic_string_view<CharT,Traits> rhs ) noexcept;
(3) (since C++17)
(until C++20)
template< class CharT, class Traits >

constexpr bool operator<=( std::basic_string_view<CharT,Traits> lhs,

                           std::basic_string_view<CharT,Traits> rhs ) noexcept;
(4) (since C++17)
(until C++20)
template< class CharT, class Traits >

constexpr bool operator>( std::basic_string_view<CharT,Traits> lhs,

                          std::basic_string_view<CharT,Traits> rhs ) noexcept;
(5) (since C++17)
(until C++20)
template< class CharT, class Traits >

constexpr bool operator>=( std::basic_string_view<CharT,Traits> lhs,

                           std::basic_string_view<CharT,Traits> rhs ) noexcept;
(6) (since C++17)
(until C++20)
template< class CharT, class Traits >

constexpr /*comp-cat*/
    operator<=>( std::basic_string_view<CharT,Traits> lhs,

                 std::basic_string_view<CharT,Traits> rhs ) noexcept;
(7) (since C++20)

Compares two views.

All comparisons are done via the compare() member function (which itself is defined in terms of Traits::compare()):

  • Two views are equal if both the size of lhs and rhs are equal and each character in lhs has an equivalent character in rhs at the same position.
  • The ordering comparisons are done lexicographically -- the comparison is performed by a function equivalent to std::lexicographical_compare.

The return type of three-way comparison operator (/*comp-cat*/) is Traits::comparison_category if it exists, std::weak_ordering otherwise.

(since C++20)

The implementation shall provide sufficient additional constexpr and noexcept overloads of these functions so that a basic_string_view<CharT,Traits> object sv may be compared to another object t with an implicit conversion to basic_string_view<CharT,Traits>, with semantics identical to comparing sv and basic_string_view<CharT,Traits>(t).

Contents

[edit] Parameters

lhs, rhs - views to compare

[edit] Return value

1-6) true if the corresponding comparison holds, false otherwise.
7) static_cast</*comp-cat*/>(lhs.compare(rhs) <=> 0).

[edit] Notes

Sufficient additional overloads can be implemented through non-deduced context in one parameter type.

Three-way comparison result type of std::string_view, std::wstring_view, std::u8string_view, std::u16string_view and std::u32string_view is std::strong_ordering.

(since C++20)

[edit] Complexity

Linear in the size of the views.