3925. Concept formattable's definition is incorrect

Section: 28.5.6.3 [format.formattable] Status: WP Submitter: Mark de Wever Opened: 2023-04-16 Last modified: 2023-11-22

Priority: Not Prioritized

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Discussion:

LWG 3631 modified the formattable concept. The new wording contains a small issue: basic_format_context requires two template arguments, but only one is provided.

[2023-05-24; Reflector poll]

Set status to Tentatively Ready after ten votes in favour during reflector poll.

[2023-06-17 Approved at June 2023 meeting in Varna. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4944.

1. Modify 28.5.6.3 [format.formattable] as indicated:

   -1- Let fmt-iter-for<charT> be an unspecified type that models output_iterator<const charT&> (24.3.4.10 [iterator.concept.output]).

   […]
   template<class T, class charT>
     concept formattable =
       formattable-with<remove_reference_t<T>, basic_format_context<fmt-iter-for<charT>, charT>>;