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Section: 20.14.4 [func.invoke] Status: Open Submitter: Great Britain Opened: 2017-02-03 Last modified: 2017-07-17
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Discussion:Addresses GB 51
The function template std::apply() in 22.214.171.124 [tuple.apply] is required to be constexpr, but std::invoke() in 20.14.4 [func.invoke] isn't. The most sensible implementation of apply_impl() is exactly equivalent to std::invoke(), so this requires implementations to have a constexpr version of invoke() for internal use, and the public API std::invoke, which must not be constexpr even though it is probably implemented in terms of the internal version.
Proposed change: Add constexpr to std::invoke.
[2017-02-20, Marshall adds wording]
We think this needs CWG 1581 to work; accepted as Immediate to resolve NB comment.
Friday: CWG 1581 was not moved in Kona. Status back to Open.
[2017-07 Toronto Tuesday PM issue prioritization]
This wording is relative to N4640.
Modify 20.14.4 [func.invoke] as indicated:
template <class F, class... Args> result_of_t<F&&(Args&&...)> invoke(F&& f, Args&&... args);