tmp/tmpqav0pvwb/{from.md → to.md}
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### Non-member comparison functions <a id="string.view.comparison">[[string.view.comparison]]</a>
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Let `S` be `basic_string_view<charT, traits>`, and `sv` be an instance
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of `S`. Implementations shall provide sufficient additional overloads
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marked `constexpr` and `noexcept` so that an object `t` with an implicit
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conversion to `S` can be compared according to
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[[string.view.comparison.overloads]].
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**Table: Additional `basic_string_view` comparison overloads** <a id="string.view.comparison.overloads">[string.view.comparison.overloads]</a>
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| Expression | Equivalent to |
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| ---------- | ------------- |
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| `t == sv` | `S(t) == sv` |
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| `sv == t` | `sv == S(t)` |
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| `t != sv` | `S(t) != sv` |
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| `sv != t` | `sv != S(t)` |
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| `t < sv` | `S(t) < sv` |
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| `sv < t` | `sv < S(t)` |
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| `t > sv` | `S(t) > sv` |
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| `sv > t` | `sv > S(t)` |
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| `t <= sv` | `S(t) <= sv` |
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| `sv <= t` | `sv <= S(t)` |
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| `t >= sv` | `S(t) >= sv` |
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| `sv >= t` | `sv >= S(t)` |
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| `t <=> sv` | `S(t) <=> sv` |
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| `sv <=> t` | `sv <=> S(t)` |
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[*Example 1*:
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A sample conforming implementation for `operator==` would be:
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``` cpp
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template<class charT, class traits>
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constexpr bool operator==(basic_string_view<charT, traits> lhs,
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basic_string_view<charT, traits> rhs) noexcept
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return lhs.compare(rhs) == 0;
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}
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template<class charT, class traits>
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constexpr bool operator==(basic_string_view<charT, traits> lhs,
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type_identity_t<basic_string_view<charT, traits>> rhs) noexcept {
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return lhs.compare(rhs) == 0;
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}
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```
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— *end example*]
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``` cpp
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template<class charT, class traits>
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constexpr bool operator==(basic_string_view<charT, traits> lhs,
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basic_string_view<charT, traits> rhs) noexcept;
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```
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*Returns:* `lhs.compare(rhs) == 0`.
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``` cpp
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template<class charT, class traits>
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constexpr see below operator<=>(basic_string_view<charT, traits> lhs,
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\itcorr basic_string_view<charT, traits> rhs) noexcept;
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```
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Let `R` denote the type `traits::comparison_category` if that
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*qualified-id* is valid and denotes a type [[temp.deduct]], otherwise
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`R` is `weak_ordering`.
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*Mandates:* `R` denotes a comparison category type [[cmp.categories]].
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*Returns:* `static_cast<R>(lhs.compare(rhs) <=> 0)`.
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### Non-member comparison functions <a id="string.view.comparison">[[string.view.comparison]]</a>
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``` cpp
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template<class charT, class traits>
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constexpr bool operator==(basic_string_view<charT, traits> lhs,
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type_identity_t<basic_string_view<charT, traits>> rhs) noexcept;
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```
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*Returns:* `lhs.compare(rhs) == 0`.
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``` cpp
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template<class charT, class traits>
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constexpr see below operator<=>(basic_string_view<charT, traits> lhs,
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\itcorr type_identity_t<basic_string_view<charT, traits>> rhs) noexcept;
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```
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Let `R` denote the type `traits::comparison_category` if that
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*qualified-id* is valid and denotes a type [[temp.deduct]], otherwise
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`R` is `weak_ordering`.
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*Mandates:* `R` denotes a comparison category type [[cmp.categories]].
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*Returns:* `static_cast<R>(lhs.compare(rhs) <=> 0)`.
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[*Note 1*: The usage of `type_identity_t` as parameter ensures that an
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object of type `basic_string_view<charT, traits>` can always be compared
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with an object of a type `T` with an implicit conversion to
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`basic_string_view<charT, traits>`, and vice versa, as per
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[[over.match.oper]]. — *end note*]
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