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3362. Strike stop_source's operator!=

Section: 32.3.5 [stopsource] Status: C++20 Submitter: Tim Song Opened: 2020-01-03 Last modified: 2021-02-25

Priority: 0

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Discussion:

Just like stop_token (see LWG 3254(i)), stop_source in 32.3.5 [stopsource] declares an operator!= friend that is unnecessary in light of the new core language rules and should be struck.

[2020-01-14 Status set to Tentatively Ready after six positive votes on the reflector.]

Proposed resolution:

This wording is relative to N4842.

  1. Modify 32.3.5 [stopsource], class stop_source synopsis, as indicated:

    namespace std {
  […]

  class stop_source {
  public:
    […]

    [[nodiscard]] friend bool
    operator==(const stop_source& lhs, const stop_source& rhs) noexcept;
    [[nodiscard]] friend bool
    operator!=(const stop_source& lhs, const stop_source& rhs) noexcept;
    friend void swap(stop_source& lhs, stop_source& rhs) noexcept;
  };
}

  2. Modify [stopsource.cmp] and [stopsource.special] as indicated:

    32.3.4.3 Non-member functionsComparisons [stopsource.nonmemberscmp] 

    [[nodiscard]] bool operator==(const stop_source& lhs, const stop_source& rhs) noexcept;

    -1- Returns: true if lhs and rhs have ownership of the same stop state or if both lhs and rhs do not have ownership of a stop state; otherwise false. 

    [[nodiscard]] bool operator!=(const stop_source& lhs, const stop_source& rhs) noexcept;

    -2- Returns: !(lhs==rhs).

    32.3.4.4 Specialized algorithms [stopsource.special] 

    friend void swap(stop_source& x, stop_source& y) noexcept;

    -1- Effects: Equivalent to: x.swap(y).