From Jason Turner

[expected.object.obs]

C++20 → C++23 2.9 KB 121 lines
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Archived: C++20 | C++23
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  1. tmp/tmptahs677y/{from.md → to.md} +118 -0
tmp/tmptahs677y/{from.md → to.md} RENAMED
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+ #### Observers <a id="expected.object.obs">[[expected.object.obs]]</a>
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+
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+ ``` cpp
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+ constexpr const T* operator->() const noexcept;
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+ constexpr T* operator->() noexcept;
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+ ```
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+
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+ *Preconditions:* `has_value()` is `true`.
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+
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+ *Returns:* `addressof(`*`val`*`)`.
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+
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+ ``` cpp
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+ constexpr const T& operator*() const & noexcept;
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+ constexpr T& operator*() & noexcept;
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+ ```
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+
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+ *Preconditions:* `has_value()` is `true`.
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+
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+ *Returns:* *val*.
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+
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+ ``` cpp
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+ constexpr T&& operator*() && noexcept;
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+ constexpr const T&& operator*() const && noexcept;
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+ ```
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+
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+ *Preconditions:* `has_value()` is `true`.
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+
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+ *Returns:* `std::move(`*`val`*`)`.
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+
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+ ``` cpp
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+ constexpr explicit operator bool() const noexcept;
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+ constexpr bool has_value() const noexcept;
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+ ```
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+
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+ *Returns:* *has_val*.
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+
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+ ``` cpp
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+ constexpr const T& value() const &;
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+ constexpr T& value() &;
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+ ```
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+
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+ *Mandates:* `is_copy_constructible_v<E>` is `true`.
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+
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+ *Returns:* *val*, if `has_value()` is `true`.
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+
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+ *Throws:* `bad_expected_access(as_const(error()))` if `has_value()` is
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+ `false`.
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+
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+ ``` cpp
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+ constexpr T&& value() &&;
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+ constexpr const T&& value() const &&;
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+ ```
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+
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+ *Mandates:* `is_copy_constructible_v<E>` is `true` and
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+ `is_constructible_v<E, decltype(std::move(error()))>` is `true`.
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+
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+ *Returns:* `std::move(`*`val`*`)`, if `has_value()` is `true`.
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+
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+ *Throws:* `bad_expected_access(std::move(error()))` if `has_value()` is
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+ `false`.
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+
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+ ``` cpp
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+ constexpr const E& error() const & noexcept;
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+ constexpr E& error() & noexcept;
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+ ```
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+
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+ *Preconditions:* `has_value()` is `false`.
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+
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+ *Returns:* *unex*.
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+
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+ ``` cpp
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+ constexpr E&& error() && noexcept;
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+ constexpr const E&& error() const && noexcept;
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+ ```
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+
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+ *Preconditions:* `has_value()` is `false`.
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+
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+ *Returns:* `std::move(`*`unex`*`)`.
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+
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+ ``` cpp
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+ template<class U> constexpr T value_or(U&& v) const &;
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+ ```
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+
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+ *Mandates:* `is_copy_constructible_v<T>` is `true` and
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+ `is_convertible_v<U, T>` is `true`.
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+
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+ *Returns:* `has_value() ? **this : static_cast<T>(std::forward<U>(v))`.
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+
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+ ``` cpp
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+ template<class U> constexpr T value_or(U&& v) &&;
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+ ```
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+
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+ *Mandates:* `is_move_constructible_v<T>` is `true` and
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+ `is_convertible_v<U, T>` is `true`.
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+
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+ *Returns:*
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+ `has_value() ? std::move(**this) : static_cast<T>(std::forward<U>(v))`.
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+
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+ ``` cpp
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+ template<class G = E> constexpr E error_or(G&& e) const &;
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+ ```
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+
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+ *Mandates:* `is_copy_constructible_v<E>` is `true` and
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+ `is_convertible_v<G, E>` is `true`.
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+
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+ *Returns:* `std::forward<G>(e)` if `has_value()` is `true`, `error()`
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+ otherwise.
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+
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+ ``` cpp
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+ template<class G = E> constexpr E error_or(G&& e) &&;
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+ ```
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+
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+ *Mandates:* `is_move_constructible_v<E>` is `true` and
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+ `is_convertible_v<G, E>` is `true`.
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+
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+ *Returns:* `std::forward<G>(e)` if `has_value()` is `true`,
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+ `std::move(error())` otherwise.
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+