22 General utilities library [utilities]

22.10 Function objects [function.objects]

22.10.5 invoke functions [func.invoke]

template<class F, class... Args>
  constexpr invoke_result_t<F, Args...> invoke(F&& f, Args&&... args)
    noexcept(is_nothrow_invocable_v<F, Args...>);

Constraints: is_invocable_v<F, Args...> is true.

Returns: INVOKE(std::forward<F>(f), std::forward<Args>(args)...) ([func.require]).

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template<class R, class F, class... Args>
  constexpr R invoke_r(F&& f, Args&&... args)
    noexcept(is_nothrow_invocable_r_v<R, F, Args...>);

Constraints: is_invocable_r_v<R, F, Args...> is true.

Returns: INVOKE<R>(std::forward<F>(f), std::forward<Args>(args)...) ([func.require]).