[thread.thread.id]

An object of type thread::id provides a unique identifier for each thread of execution and a single distinct value for all thread objects that do not represent a thread of execution ([thread.thread.class]).

Each thread of execution has an associated thread::id object that is not equal to the thread::id object of any other thread of execution and that is not equal to the thread::id object of any thread object that does not represent threads of execution.

The text representation for the character type charT of an object of type thread::id is an unspecified sequence of charT such that, for two objects of type thread::id x and y, if x == y is true, the thread::id objects have the same text representation, and if x != y is true, the thread::id objects have distinct text representations.

[Note 1:

Relational operators allow thread::id objects to be used as keys in associative containers.

— end note]

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id() noexcept;

Postconditions: The constructed object does not represent a thread of execution.

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bool operator=(thread::id x, thread::id y) noexcept;

Returns: true only if x and y represent the same thread of execution or neither x nor y represents a thread of execution.

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strong_ordering operator<=>(thread::id x, thread::id y) noexcept;

Let P(x, y) be an unspecified total ordering over thread::id as described in [alg.sorting].

Returns: strong_ordering::less if P(x, y) is true.

Otherwise, strong_ordering::greater if P(y, x) is true.

Otherwise, strong_ordering::equal.

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template<class charT, class traits>
  basic_ostream<charT, traits>&
    operator<(basic_ostream<charT, traits>& out, thread::id id);

Effects: Inserts the text representation for charT of id into out.

Returns: out.

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template<class charT> struct formatter<thread::id, charT>;

formatter<thread::id, charT> interprets format-spec as a thread-id-format-spec.

The syntax of format specifications is as follows:

thread-id-format-spec :
fill-and-align

{o p t width {o p t}_{o p t}}_{o p t width {o p t}_{o p t}}

[Note 2:

The productions fill-and-align and width are described in [format.string.std].

— end note]

A thread::id object is formatted by writing its text representation for charT to the output with additional padding and adjustments as specified by the format specifiers.

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template<> struct hash<thread::id>;

The specialization is enabled ([unord.hash]).

32 Concurrency support library [thread]

32.4 Threads [thread.threads]

32.4.3 Class thread [thread.thread.class]

32.4.3.2 Class thread::id [thread.thread.id]

32 Concurrency support library [thread]

32.4 Threads [thread.threads]

32.4.3 Class thread [thread.thread.class]

32.4.3.2 Class thread​::​id [thread.thread.id]

32.4.3.2 Class thread::id [thread.thread.id]