24 Strings library [strings]

24.4 String view classes [string.view]

24.4.3 Non-member comparison functions [string.view.comparison]

1
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Let S be basic_­string_­view<charT, traits>, and sv be an instance of S. Implementations shall provide sufficient additional overloads marked constexpr and noexcept so that an object t with an implicit conversion to S can be compared according to Table 67.

Table 67 — Additional basic_­string_­view comparison overloads
ExpressionEquivalent to
t == sv S(t) == sv
sv == t sv == S(t)
t != sv S(t) != sv
sv != t sv != S(t)
t < sv S(t) < sv
sv < t sv < S(t)
t > sv S(t) > sv
sv > t sv > S(t)
t <= sv S(t) <= sv
sv <= t sv <= S(t)
t >= sv S(t) >= sv
sv >= t sv >= S(t)

[ Example: A sample conforming implementation for operator== would be: 

template<class T> using __identity = decay_t<T>;
template<class charT, class traits>
  constexpr bool operator==(basic_string_view<charT, traits> lhs,
                            basic_string_view<charT, traits> rhs) noexcept {
    return lhs.compare(rhs) == 0;
  }
template<class charT, class traits>
  constexpr bool operator==(basic_string_view<charT, traits> lhs,
                            __identity<basic_string_view<charT, traits>> rhs) noexcept {
    return lhs.compare(rhs) == 0;
  }
template<class charT, class traits>
  constexpr bool operator==(__identity<basic_string_view<charT, traits>> lhs,
                            basic_string_view<charT, traits> rhs) noexcept {
    return lhs.compare(rhs) == 0;
  }

 — end example ]

template<class charT, class traits> constexpr bool operator==(basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

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Returns: lhs.compare(rhs) == 0.

template<class charT, class traits> constexpr bool operator!=(basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

3
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Returns: lhs.compare(rhs) != 0.

template<class charT, class traits> constexpr bool operator< (basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

4
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Returns: lhs.compare(rhs) < 0.

template<class charT, class traits> constexpr bool operator> (basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

5
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Returns: lhs.compare(rhs) > 0.

template<class charT, class traits> constexpr bool operator<=(basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

6
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Returns: lhs.compare(rhs) <= 0.

template<class charT, class traits> constexpr bool operator>=(basic_string_view<charT, traits> lhs, basic_string_view<charT, traits> rhs) noexcept;

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Returns: lhs.compare(rhs) >= 0.