libcxx/include/__format/concepts.h

   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_CONCEPTS_H
  11 #define _LIBCPP___FORMAT_CONCEPTS_H
  12
  13 #include <__concepts/same_as.h>
  14 #include <__concepts/semiregular.h>
  15 #include <__config>
  16 #include <__format/format_fwd.h>
  17 #include <__format/format_parse_context.h>
  18 #include <__type_traits/is_specialization.h>
  19 #include <__type_traits/remove_const.h>
  20 #include <__utility/pair.h>
  21 #include <tuple>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28
  29 #if _LIBCPP_STD_VER >= 20
  30
  31 /// The character type specializations of \ref formatter.
  32 template <class _CharT>
  33 concept __fmt_char_type =
  34     same_as<_CharT, char>
  35 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
  36     || same_as<_CharT, wchar_t>
  37 #  endif
  38     ;
  39
  40 // The output iterator isn't specified. A formatter should accept any
  41 // output_iterator. This iterator is a minimal iterator to test the concept.
  42 // (Note testing for (w)format_context would be a valid choice, but requires
  43 // selecting the proper one depending on the type of _CharT.)
  44 template <class _CharT>
  45 using __fmt_iter_for = _CharT*;
  46
  47 template <class _Tp, class _Context, class _Formatter = typename _Context::template formatter_type<remove_const_t<_Tp>>>
  48 concept __formattable_with =
  49     semiregular<_Formatter> &&
  50     requires(_Formatter& __f,
  51              const _Formatter& __cf,
  52              _Tp&& __t,
  53              _Context __fc,
  54              basic_format_parse_context<typename _Context::char_type> __pc) {
  55       { __f.parse(__pc) } -> same_as<typename decltype(__pc)::iterator>;
  56       { __cf.format(__t, __fc) } -> same_as<typename _Context::iterator>;
  57     };
  58
  59 template <class _Tp, class _CharT>
  60 concept __formattable =
  61     __formattable_with<remove_reference_t<_Tp>, basic_format_context<__fmt_iter_for<_CharT>, _CharT>>;
  62
  63 #  if _LIBCPP_STD_VER >= 23
  64 template <class _Tp, class _CharT>
  65 concept formattable = __formattable<_Tp, _CharT>;
  66
  67 // [tuple.like] defines a tuple-like exposition only concept. This concept is
  68 // not related to that. Therefore it uses a different name for the concept.
  69 //
  70 // TODO FMT Add a test to validate we fail when using that concept after P2165
  71 // has been implemented.
  72 template <class _Tp>
  73 concept __fmt_pair_like =
  74     __is_specialization_v<_Tp, pair> || (__is_specialization_v<_Tp, tuple> && tuple_size_v<_Tp> == 2);
  75
  76 #  endif //_LIBCPP_STD_VER >= 23
  77 #endif //_LIBCPP_STD_VER >= 20
  78
  79 _LIBCPP_END_NAMESPACE_STD
  80
  81 #endif // _LIBCPP___FORMAT_CONCEPTS_H