1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___FORMAT_FORMATTABLE_H
11#define _LIBCPP___FORMAT_FORMATTABLE_H
12
13#include <__concepts/same_as.h>
14#include <__concepts/semiregular.h>
15#include <__config>
16#include <__format/format_parse_context.h>
17#include <__fwd/format.h>
18#include <__type_traits/remove_const.h>
19#include <__type_traits/remove_reference.h>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22# pragma GCC system_header
23#endif
24
25#if _LIBCPP_STD_VER >= 20
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29// The output iterator isn't specified. A formatter should accept any
30// output_iterator. This iterator is a minimal iterator to test the concept.
31// (Note testing for (w)format_context would be a valid choice, but requires
32// selecting the proper one depending on the type of _CharT.)
33template <class _CharT>
34using __fmt_iter_for _LIBCPP_NODEBUG = _CharT*;
35
36template <class _Tp, class _Context, class _Formatter = typename _Context::template formatter_type<remove_const_t<_Tp>>>
37concept __formattable_with =
38 semiregular<_Formatter> &&
39 requires(_Formatter& __f,
40 const _Formatter& __cf,
41 _Tp&& __t,
42 _Context __fc,
43 basic_format_parse_context<typename _Context::char_type> __pc) {
44 { __f.parse(__pc) } -> same_as<typename decltype(__pc)::iterator>;
45 { __cf.format(__t, __fc) } -> same_as<typename _Context::iterator>;
46 };
47
48template <class _Tp, class _CharT>
49concept __formattable =
50 __formattable_with<remove_reference_t<_Tp>, basic_format_context<__fmt_iter_for<_CharT>, _CharT>>;
51
52# if _LIBCPP_STD_VER >= 23
53template <class _Tp, class _CharT>
54concept formattable = __formattable<_Tp, _CharT>;
55# endif // _LIBCPP_STD_VER >= 23
56
57_LIBCPP_END_NAMESPACE_STD
58
59#endif // _LIBCPP_STD_VER >= 20
60
61#endif // _LIBCPP___FORMAT_FORMATTABLE_H
62