22 General utilities library [utilities]

22.8 Expected objects [expected]

22.8.7 Partial specialization of expected for void types [expected.void]

22.8.7.2 Constructors [expected.void.cons]

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constexpr expected() noexcept;
1
#
Postconditions: has_value() is true.
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constexpr expected(const expected& rhs);
2
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Effects: If rhs.has_value() is false, direct-non-list-initializes unex with rhs.error().
3
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Postconditions: rhs.has_value() == this->has_value().
4
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Throws: Any exception thrown by the initialization of unex.
5
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Remarks: This constructor is defined as deleted unless is_copy_constructible_v<E> is true.
6
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This constructor is trivial if is_trivially_copy_constructible_v<E> is true.
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constexpr expected(expected&& rhs) noexcept(is_nothrow_move_constructible_v<E>);
7
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Constraints: is_move_constructible_v<E> is true.
8
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Effects: If rhs.has_value() is false, direct-non-list-initializes unex with std​::​move(rhs.error()).
9
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Postconditions: rhs.has_value() is unchanged; rhs.has_value() == this->has_value() is true.
10
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Throws: Any exception thrown by the initialization of unex.
11
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Remarks: This constructor is trivial if is_trivially_move_constructible_v<E> is true.
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template<class U, class G> constexpr explicit(!is_convertible_v<const G&, E>) expected(const expected<U, G>& rhs); template<class U, class G> constexpr explicit(!is_convertible_v<G, E>) expected(expected<U, G>&& rhs);
12
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Let GF be const G& for the first overload and G for the second overload.
13
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Constraints:
  • (13.1)
    is_void_v<U> is true; and
  • (13.2)
    is_constructible_v<E, GF> is true; and
  • (13.3)
    is_constructible_v<unexpected<E>, expected<U, G>&> is false; and
  • (13.4)
    is_constructible_v<unexpected<E>, expected<U, G>> is false; and
  • (13.5)
    is_constructible_v<unexpected<E>, const expected<U, G>&> is false; and
  • (13.6)
    is_constructible_v<unexpected<E>, const expected<U, G>> is false.
14
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Effects: If rhs.has_value() is false, direct-non-list-initializes unex with std​::​forward<GF>(rhs.error()).
15
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Postconditions: rhs.has_value() is unchanged; rhs.has_value() == this->has_value() is true.
16
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Throws: Any exception thrown by the initialization of unex.
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template<class G> constexpr explicit(!is_convertible_v<const G&, E>) expected(const unexpected<G>& e); template<class G> constexpr explicit(!is_convertible_v<G, E>) expected(unexpected<G>&& e);
17
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Let GF be const G& for the first overload and G for the second overload.
18
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Constraints: is_constructible_v<E, GF> is true.
19
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Effects: Direct-non-list-initializes unex with std​::​forward<GF>(e.error()).
20
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Postconditions: has_value() is false.
21
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Throws: Any exception thrown by the initialization of unex.
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constexpr explicit expected(in_place_t) noexcept;
22
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Postconditions: has_value() is true.
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template<class... Args> constexpr explicit expected(unexpect_t, Args&&... args);
23
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Constraints: is_constructible_v<E, Args...> is true.
24
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Effects: Direct-non-list-initializes unex with std​::​forward<Args>(args)....
25
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Postconditions: has_value() is false.
26
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Throws: Any exception thrown by the initialization of unex.
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template<class U, class... Args> constexpr explicit expected(unexpect_t, initializer_list<U> il, Args&&... args);
27
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Constraints: is_constructible_v<E, initializer_list<U>&, Args...> is true.
28
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Effects: Direct-non-list-initializes unex with il, std​::​forward<Args>(args)....
29
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Postconditions: has_value() is false.
30
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Throws: Any exception thrown by the initialization of unex.