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Difference between revisions of "cpp/header/format"

From cppreference.com
< cpp‎ | header
(updated sypnosis)
(Header content update as per P3107R5.)
 
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−
{{cpp/header/title|format}}
+
{{cpp/header/title|format|notes={{mark c++20}}}}
 
{{cpp/header/navbar}}
 
{{cpp/header/navbar}}
  
Line 5: Line 5:
  
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc h1 | Classes}}
+
{{dsc h1|Concepts}}
−
{{dsc inc | cpp/utility/format/dsc formatter}}
+
{{dsc inc|cpp/utility/format/dsc formattable}}
−
{{dsc inc | cpp/utility/format/dsc basic_format_parse_context}}
+
{{dsc h1|Enumerations}}
−
{{dsc inc | cpp/utility/format/dsc basic_format_context}}
+
{{dsc inc|cpp/utility/format/dsc range_format}}
−
{{dsc inc | cpp/utility/format/dsc basic_format_arg}}
+
{{dsc h1|Classes}}
−
{{dsc inc | cpp/utility/format/dsc basic_format_args}}
+
{{dsc inc|cpp/utility/format/dsc formatter}}
−
{{dsc inc | cpp/utility/format/dsc format_error}}
+
{{dsc inc|cpp/utility/format/dsc range_formatter}}
−
{{dsc h1 | Functions}}
+
{{dsc inc|cpp/utility/format/dsc basic_format_parse_context}}
−
{{dsc inc | cpp/utility/format/dsc format}}
+
{{dsc inc|cpp/utility/format/dsc basic_format_context}}
−
{{dsc inc | cpp/utility/format/dsc format_to}}
+
{{dsc inc|cpp/utility/format/dsc basic_format_arg}}
−
{{dsc inc | cpp/utility/format/dsc format_to_n}} <!-- include result type inside -->
+
{{dsc inc|cpp/utility/format/dsc basic_format_args}}
−
{{dsc inc | cpp/utility/format/dsc formatted_size}}
+
{{dsc inc|cpp/utility/format/dsc basic_format_string}}
−
{{dsc inc | cpp/utility/format/dsc vformat}}
+
{{dsc inc|cpp/utility/format/dsc format_error}}
−
{{dsc inc | cpp/utility/format/dsc vformat_to}}
+
{{dsc h2|Formatter specializations}}
−
{{dsc inc | cpp/utility/format/dsc visit_format_arg}}
+
{{dsc inc|cpp/utility/format/dsc tuple_formatter}}
−
{{dsc inc | cpp/utility/format/dsc make_format_args}}
+
{{dsc inc|cpp/utility/format/dsc ranges_formatter}}
 +
{{dsc h1|Functions}}
 +
{{dsc inc|cpp/utility/format/dsc format}}
 +
{{dsc inc|cpp/utility/format/dsc format_to}}
 +
{{dsc inc|cpp/utility/format/dsc format_to_n}} <!-- include result type inside -->
 +
{{dsc inc|cpp/utility/format/dsc formatted_size}}
 +
{{dsc inc|cpp/utility/format/dsc runtime_format}}
 +
{{dsc inc|cpp/utility/format/dsc vformat}}
 +
{{dsc inc|cpp/utility/format/dsc vformat_to}}
 +
{{dsc inc|cpp/utility/format/dsc visit_format_arg}}
 +
{{dsc inc|cpp/utility/format/dsc make_format_args}}
 +
{{dsc h1|Helpers}}
 +
{{dsc inc|cpp/utility/format/dsc format_kind}}
 +
{{dsc inc|cpp/utility/format/dsc enable_nonlocking_formatter_optimization}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Synopsis===
 
===Synopsis===
−
{{source|1=
+
{{cpp/synopsis/format}}
−
namespace std {
+
−
  // basic format string
+
−
  template<class charT, class... Args> struct /*basic-format-string*/; // exposition only
+
  
−
  template<class... Args>
+
{{langlinks|de|es|fr|ko|ja|ru|zh}}
−
    using /*format-string*/
+
−
    = /*basic-format-string*/<char, type_identity_t<Args>...>; // exposition only
+
−
  template<class... Args>
+
−
    using /*wformat-string*/
+
−
    = /*basic-format-string*/<wchar_t, type_identity_t<Args>...>; // exposition only
+
−
 
+
−
  // formatting functions
+
−
  template<class... Args>
+
−
    string format(/*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    wstring format(/*wformat-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    string format(const locale& loc,
+
−
                  /*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    wstring format(const locale& loc,
+
−
                  /*wformat-string*/<Args...> fmt, Args&&... args);
+
−
 
+
−
  string vformat(string_view fmt, format_args args);
+
−
  wstring vformat(wstring_view fmt, wformat_args args);
+
−
  string vformat(const locale& loc, string_view fmt, format_args args);
+
−
  wstring vformat(const locale& loc, wstring_view fmt, wformat_args args);
+
−
 
+
−
  template<class Out, class... Args>
+
−
    Out format_to(Out out, /*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    Out format_to(Out out, /*wformat-string*/<Args...> fmt, Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    Out format_to(Out out, const locale& loc,
+
−
                  /*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    Out format_to(Out out, const locale& loc,
+
−
                  /*wformat-string*/<Args...> fmt, Args&&... args);
+
−
 
+
−
  template<class Out>
+
−
    Out vformat_to(Out out, string_view fmt, format_args args);
+
−
  template<class Out>
+
−
    Out vformat_to(Out out, wstring_view fmt, wformat_args args);
+
−
  template<class Out>
+
−
    Out vformat_to(Out out, const locale& loc, string_view fmt, format_args args);
+
−
  template<class Out>
+
−
    Out vformat_to(Out out, const locale& loc, wstring_view fmt, wformat_args args);
+
−
 
+
−
  template<class Out> struct format_to_n_result {
+
−
    Out out;
+
−
    iter_difference_t<Out> size;
+
−
  };
+
−
  template<class Out, class... Args>
+
−
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
+
−
                                        /*format-string*/<Args...> fmt,
+
−
                                        Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
+
−
                                        /*wformat-string*/<Args...> fmt,
+
−
                                        Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
+
−
                                        const locale& loc,
+
−
                                        /*format-string*/<Args...> fmt,
+
−
                                        Args&&... args);
+
−
  template<class Out, class... Args>
+
−
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
+
−
                                        const locale& loc,
+
−
                                        /*wformat-string*/<Args...> fmt,
+
−
                                        Args&&... args);
+
−
 
+
−
  template<class... Args>
+
−
    size_t formatted_size(/*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    size_t formatted_size(/*wformat-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    size_t formatted_size(const locale& loc,
+
−
                          /*format-string*/<Args...> fmt, Args&&... args);
+
−
  template<class... Args>
+
−
    size_t formatted_size(const locale& loc,
+
−
                          /*wformat-string*/<Args...> fmt, Args&&... args);
+
−
 
+
−
  // formatter
+
−
  template<class T, class charT = char> struct formatter;
+
−
 
+
−
  // class template basic_format_parse_context
+
−
  template<class charT> class basic_format_parse_context;
+
−
  using format_parse_context = basic_format_parse_context<char>;
+
−
  using wformat_parse_context = basic_format_parse_context<wchar_t>;
+
−
 
+
−
  template<class Out, class charT> class basic_format_context;
+
−
  using format_context = basic_format_context</*unspecified*/, char>;
+
−
  using wformat_context = basic_format_context</*unspecified*/, wchar_t>;
+
−
 
+
−
  // arguments
+
−
  // class template basic_format_arg
+
−
  template<class Context> class basic_format_arg;
+
−
 
+
−
  template<class Visitor, class Context>
+
−
    /* see description */ visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
+
−
 
+
−
  // class template format-arg-store
+
−
  template<class Context, class... Args> struct /*format-arg-store*/;  // exposition only
+
−
 
+
−
  template<class Context = format_context, class... Args>
+
−
    /*format-arg-store*/<Context, Args...>
+
−
      make_format_args(Args&&... args);
+
−
  template<class... Args>
+
−
    /*format-arg-store*/<wformat_context, Args...>
+
−
      make_wformat_args(Args&&... args);
+
−
 
+
−
  // class template basic_format_args
+
−
  template<class Context> class basic_format_args;
+
−
  using format_args = basic_format_args<format_context>;
+
−
  using wformat_args = basic_format_args<wformat_context>;
+
−
 
+
−
  // class format_error
+
−
  class format_error;
+
−
}
+
−
}}
+
−
 
+
−
====Class template ''{{tt|basic-format-string}}''====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class charT, class... Args>
+
−
  struct /*basic-format-string*/ {  // exposition only
+
−
  private:
+
−
    basic_string_view<charT> str_;  // exposition only
+
−
 
+
−
  public:
+
−
    template<class T> consteval /*basic-format-string*/(const T& s);
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class template {{lc|std::basic_format_parse_context}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class charT>
+
−
  class basic_format_parse_context {
+
−
  public:
+
−
    using char_type = charT;
+
−
    using const_iterator = typename basic_string_view<charT>::const_iterator;
+
−
    using iterator = const_iterator;
+
−
 
+
−
  private:
+
−
    iterator begin_;                                    // exposition only
+
−
    iterator end_;                                      // exposition only
+
−
    enum indexing { unknown, manual, automatic };      // exposition only
+
−
    indexing indexing_;                                // exposition only
+
−
    size_t next_arg_id_;                                // exposition only
+
−
    size_t num_args_;                                  // exposition only
+
−
 
+
−
  public:
+
−
    constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
+
−
                                                  size_t num_args = 0) noexcept;
+
−
    basic_format_parse_context(const basic_format_parse_context&) = delete;
+
−
    basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
+
−
 
+
−
    constexpr const_iterator begin() const noexcept;
+
−
    constexpr const_iterator end() const noexcept;
+
−
    constexpr void advance_to(const_iterator it);
+
−
 
+
−
    constexpr size_t next_arg_id();
+
−
    constexpr void check_arg_id(size_t id);
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class template {{lc|std::basic_format_context}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class Out, class charT>
+
−
  class basic_format_context {
+
−
    basic_format_args<basic_format_context> args_;      // exposition only
+
−
    Out out_;                                          // exposition only
+
−
 
+
−
  public:
+
−
    using iterator = Out;
+
−
    using char_type = charT;
+
−
    template<class T> using formatter_type = formatter<T, charT>;
+
−
 
+
−
    basic_format_arg<basic_format_context> arg(size_t id) const;
+
−
    std::locale locale();
+
−
 
+
−
    iterator out();
+
−
    void advance_to(iterator it);
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class template {{lc|std::basic_format_arg}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class Context>
+
−
  class basic_format_arg {
+
−
  public:
+
−
    class handle;
+
−
 
+
−
  private:
+
−
    using char_type = typename Context::char_type;                    // exposition only
+
−
 
+
−
    variant<monostate, bool, char_type,
+
−
            int, unsigned int, long long int, unsigned long long int,
+
−
            float, double, long double,
+
−
            const char_type*, basic_string_view<char_type>,
+
−
            const void*, handle> value;                                // exposition only
+
−
 
+
−
    template<class T> explicit basic_format_arg(T&& v) noexcept;  // exposition only
+
−
    explicit basic_format_arg(float n) noexcept;                      // exposition only
+
−
    explicit basic_format_arg(double n) noexcept;                      // exposition only
+
−
    explicit basic_format_arg(long double n) noexcept;                // exposition only
+
−
    explicit basic_format_arg(const char_type* s);                    // exposition only
+
−
 
+
−
    template<class traits>
+
−
      explicit basic_format_arg(
+
−
        basic_string_view<char_type, traits> s) noexcept;              // exposition only
+
−
 
+
−
    template<class traits, class Allocator>
+
−
      explicit basic_format_arg(
+
−
        const basic_string<char_type, traits, Allocator>& s) noexcept; // exposition only
+
−
 
+
−
    explicit basic_format_arg(nullptr_t) noexcept;                    // exposition only
+
−
 
+
−
    template<class T>
+
−
      explicit basic_format_arg(const T* p) noexcept;                  // exposition only
+
−
 
+
−
  public:
+
−
    basic_format_arg() noexcept;
+
−
 
+
−
    explicit operator bool() const noexcept;
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class {{lc|std::basic_format_arg::handle}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class Context>
+
−
  class basic_format_arg<Context>::handle {
+
−
    const void* ptr_;                                          // exposition only
+
−
    void (*format_)(basic_format_parse_context<char_type>&,
+
−
                    Context&, const void*);                    // exposition only
+
−
 
+
−
    template<class T> explicit handle(T&& val) noexcept;  // exposition only
+
−
 
+
−
    friend class basic_format_arg<Context>;                    // exposition only
+
−
 
+
−
  public:
+
−
    void format(basic_format_parse_context<char_type>&, Context& ctx) const;
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class template ''{{tt|format-arg-store}}''====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class Context, class... Args>
+
−
  struct /*format-arg-store*/ {      // exposition only
+
−
    array<basic_format_arg<Context>, sizeof...(Args)> args;
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class template {{lc|std::basic_format_args}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  template<class Context>
+
−
  class basic_format_args {
+
−
    size_t size_;                              // exposition only
+
−
    const basic_format_arg<Context>* data_;    // exposition only
+
−
 
+
−
  public:
+
−
    basic_format_args() noexcept;
+
−
 
+
−
    template<class... Args>
+
−
      basic_format_args(const /*format-arg-store*/<Context, Args...>& store) noexcept;
+
−
 
+
−
    basic_format_arg<Context> get(size_t i) const noexcept;
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
====Class {{lc|std::format_error}}====
+
−
{{source|1=
+
−
namespace std {
+
−
  class format_error : public runtime_error {
+
−
  public:
+
−
    explicit format_error(const string& what_arg);
+
−
    explicit format_error(const char* what_arg);
+
−
  };
+
−
}
+
−
}}
+
−
 
+
−
{{langlinks|es|ja|zh}}
+

Latest revision as of 17:39, 28 April 2024

 
C++
 
Standard library headers
General utilities
<any> (C++17)
<bitset>
<bit> (C++20)
<charconv> (C++17)
<expected> (C++23)
<format> (C++20)
<functional>
<optional> (C++17)
<tuple> (C++11)
<typeindex> (C++11)
<utility>
<variant> (C++17)
Containers
<array> (C++11)
<deque>
<flat_map> (C++23)
<flat_set> (C++23)
<forward_list> (C++11)
<inplace_vector> (C++26)   
<list>
<map>
<mdspan> (C++23)
<queue>
<set>
<span> (C++20)
<stack>
<unordered_map> (C++11)
<unordered_set> (C++11)
<vector>
Iterators
<iterator>
Ranges
<generator> (C++23)
<ranges> (C++20)
 

This header is part of the format library.

Contents

Concepts

(C++23)
 specifies that a type is formattable, that is, it specializes std::formatter and provides member functions parse and format
(concept) [edit]

Enumerations

(C++23)
 specifies how a range should be formatted
(enum) [edit]

Classes

(C++20)
 defines formatting rules for a given type
(class template) [edit]
(C++23)
 class template that helps implementing std::formatter specializations for range types
(class template) [edit]
(C++20)(C++20)(C++20)
 formatting string parser state
(class template) [edit]
(C++20)(C++20)(C++20)
 formatting state, including all formatting arguments and the output iterator
(class template) [edit]
(C++20)
 class template that provides access to a formatting argument for user-defined formatters
(class template) [edit]
(C++20)(C++20)(C++20)
 class that provides access to all formatting arguments
(class template) [edit]
(C++20)(C++20)(C++20)
 class template that performs compile-time format string checks at construction time
(class template) [edit]
(C++20)
 exception type thrown on formatting errors
(class) [edit]
Formatter specializations
(C++23)
 formatting support for pair and tuple
(class template specialization) [edit]
(C++23)
 formatting support for ranges
(class template specialization) [edit]

Functions

(C++20)
 stores formatted representation of the arguments in a new string
(function template) [edit]
(C++20)
 writes out formatted representation of its arguments through an output iterator
(function template) [edit]
(C++20)
 writes out formatted representation of its arguments through an output iterator, not exceeding specified size
(function template) [edit]
(C++20)
 determines the number of characters necessary to store the formatted representation of its arguments
(function template) [edit]
(C++26)
 creates runtime format strings directly usable in user-oriented formatting functions
(function) [edit]
(C++20)
 non-template variant of std::format using type-erased argument representation
(function) [edit]
(C++20)
 non-template variant of std::format_to using type-erased argument representation
(function template) [edit]
(C++20) (deprecated in C++26)
 argument visitation interface for user-defined formatters
(function template) [edit]
(C++20)(C++20)
 creates a type-erased object referencing all formatting arguments, convertible to format_args
(function template) [edit]

Helpers

(C++23)
 selects a suited std::range_format for a range
(variable template)[edit]
(C++23)
 indicates the argument type can be efficiently printed
(variable template)[edit]

[edit] Synopsis

namespace std {
  // class template basic_format_context
  template<class Out, class CharT> class basic_format_context;
  using format_context = basic_format_context</* unspecified */, char>;
  using wformat_context = basic_format_context</* unspecified */, wchar_t>;
 
  // class template basic_format_args
  template<class Context> class basic_format_args;
  using format_args = basic_format_args<format_context>;
  using wformat_args = basic_format_args<wformat_context>;
 
  // class template basic_format_string
  template<class CharT, class... Args>
    struct basic_format_string;
 
  template<class... Args>
    using format_string = basic_format_string<char, type_identity_t<Args>...>;
  template<class... Args>
    using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
 
  // formatting functions
  template<class... Args>
    string format(format_string<Args...> fmt, Args&&... args);
  template<class... Args>
    wstring format(wformat_string<Args...> fmt, Args&&... args);
  template<class... Args>
    string format(const locale& loc, format_string<Args...> fmt, Args&&... args);
  template<class... Args>
    wstring format(const locale& loc, wformat_string<Args...> fmt, Args&&... args);
 
  string vformat(string_view fmt, format_args args);
  wstring vformat(wstring_view fmt, wformat_args args);
  string vformat(const locale& loc, string_view fmt, format_args args);
  wstring vformat(const locale& loc, wstring_view fmt, wformat_args args);
 
  template<class Out, class... Args>
    Out format_to(Out out, format_string<Args...> fmt, Args&&... args);
  template<class Out, class... Args>
    Out format_to(Out out, wformat_string<Args...> fmt, Args&&... args);
  template<class Out, class... Args>
    Out format_to(Out out, const locale& loc, format_string<Args...> fmt, Args&&... args);
  template<class Out, class... Args>
    Out format_to(Out out, const locale& loc, wformat_string<Args...> fmt, Args&&... args);
 
  template<class Out>
    Out vformat_to(Out out, string_view fmt, format_args args);
  template<class Out>
    Out vformat_to(Out out, wstring_view fmt, wformat_args args);
  template<class Out>
    Out vformat_to(Out out, const locale& loc, string_view fmt, format_args args);
  template<class Out>
    Out vformat_to(Out out, const locale& loc, wstring_view fmt, wformat_args args);
 
  template<class Out> struct format_to_n_result {
    Out out;
    iter_difference_t<Out> size;
  };
  template<class Out, class... Args>
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
                                        format_string<Args...> fmt, Args&&... args);
  template<class Out, class... Args>
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
                                        wformat_string<Args...> fmt, Args&&... args);
  template<class Out, class... Args>
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
                                        const locale& loc, format_string<Args...> fmt,
                                        Args&&... args);
  template<class Out, class... Args>
    format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
                                        const locale& loc, wformat_string<Args...> fmt,
                                        Args&&... args);
 
  template<class... Args>
    size_t formatted_size(format_string<Args...> fmt, Args&&... args);
  template<class... Args>
    size_t formatted_size(wformat_string<Args...> fmt, Args&&... args);
  template<class... Args>
    size_t formatted_size(const locale& loc, format_string<Args...> fmt, Args&&... args);
  template<class... Args>
    size_t formatted_size(const locale& loc, wformat_string<Args...> fmt, Args&&... args);
 
  // formatter
  template<class T, class CharT = char>
    struct formatter;
 
  // variable template enable_nonlocking_formatter_optimization
  template<class T>
    constexpr bool enable_nonlocking_formatter_optimization = false;
 
  // concept formattable
  template<class T, class CharT>
    concept formattable = /* see description */;
 
  template<class R, class CharT>
    concept __const_formattable_range =                               // exposition only
      ranges::input_range<const R> &&
      formattable<ranges::range_reference_t<const R>, CharT>;
 
  template<class R, class CharT>
    using __fmt_maybe_const =                                         // exposition only
      conditional_t<__const_formattable_range<R, CharT>, const R, R>;
 
  // class template basic_format_parse_context
  template<class CharT> class basic_format_parse_context;
  using format_parse_context = basic_format_parse_context<char>;
  using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
  // formatting of ranges
  // variable template format_kind
  enum class range_format {
    disabled,
    map,
    set,
    sequence,
    string,
    debug_string
  };
 
  template<class R>
    constexpr /* unspecified */ format_kind = /* unspecified */;
 
  template<ranges::input_range R>
      requires same_as<R, remove_cvref_t<R>>
    constexpr range_format format_kind<R> = /* see description */;
 
  // class template range_formatter
  template<class T, class CharT = char>
    requires same_as<remove_cvref_t<T>, T> && formattable<T, CharT>
  class range_formatter;
 
  // class template range-default-formatter
  template<range_format K, ranges::input_range R, class CharT>
    struct __range_default_formatter;                                 // exposition only
 
  // specializations for maps, sets, and strings
  template<ranges::input_range R, class CharT>
    requires (format_kind<R> != range_format::disabled) &&
             formattable<ranges::range_reference_t<R>, CharT>
  struct formatter<R, CharT> : __range_default_formatter<format_kind<R>, R, CharT> { };
 
  // arguments
  // class template basic_format_arg
  template<class Context> class basic_format_arg;
 
  template<class Visitor, class Context>
    decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
 
  // class template format-arg-store
  template<class Context, class... Args> class __format_arg_store;    // exposition only
 
  template<class Context = format_context, class... Args>
    __format_arg_store<Context, Args...>
      make_format_args(Args&&... fmt_args);
  template<class... Args>
    __format_arg_store<wformat_context, Args...>
      make_wformat_args(Args&&... args);
 
  // class format_error
  class format_error;
}

[edit] Class template std::basic_format_string

namespace std {
  template<class CharT, class... Args>
  struct basic_format_string {
  private:
    basic_string_view<CharT> str;         // exposition only
 
  public:
    template<class T> consteval basic_format_string(const T& s);
 
    constexpr basic_string_view<CharT> get() const noexcept { return str; }
  };
}

[edit] Concept std::formattable

template<class T, class CharT>
  concept formattable =
    semiregular<formatter<remove_cvref_t<T>, CharT>> &&
    requires(formatter<remove_cvref_t<T>, CharT> f,
             const formatter<remove_cvref_t<T>, CharT> cf,
             T t,
             basic_format_context<__fmt_iter_for<CharT>, CharT> fc,
             basic_format_parse_context<CharT> pc) {
        { f.parse(pc) } -> same_as<basic_format_parse_context<CharT>::iterator>;
        { cf.format(t, fc) } -> same_as<__fmt_iter_for<CharT>>;
    };

[edit] Class template std::basic_format_parse_context

namespace std {
  template<class CharT>
  class basic_format_parse_context {
  public:
    using char_type = CharT;
    using const_iterator = typename basic_string_view<CharT>::const_iterator;
    using iterator = const_iterator;
 
  private:
    iterator begin_;                                    // exposition only
    iterator end_;                                      // exposition only
    enum indexing { unknown, manual, automatic };       // exposition only
    indexing indexing_;                                 // exposition only
    size_t next_arg_id_;                                // exposition only
    size_t num_args_;                                   // exposition only
 
  public:
    constexpr explicit basic_format_parse_context(basic_string_view<CharT> fmt,
                                                  size_t num_args = 0) noexcept;
    basic_format_parse_context(const basic_format_parse_context&) = delete;
    basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
 
    constexpr const_iterator begin() const noexcept;
    constexpr const_iterator end() const noexcept;
    constexpr void advance_to(const_iterator it);
 
    constexpr size_t next_arg_id();
    constexpr void check_arg_id(size_t id);
 
    template<class... Ts>
    constexpr void check_dynamic_spec(size_t id) noexcept;
    constexpr void check_dynamic_spec_integral(size_t id) noexcept;
    constexpr void check_dynamic_spec_string(size_t id) noexcept;
  };
}

[edit] Class template std::basic_format_context

namespace std {
  template<class Out, class CharT>
  class basic_format_context {
    basic_format_args<basic_format_context> args_;      // exposition only
    Out out_;                                           // exposition only
 
    basic_format_context(const basic_format_context&) = delete;
    basic_format_context& operator=(const basic_format_context&) = delete;
 
  public:
    using iterator = Out;
    using char_type = CharT;
    template<class T> using formatter_type = formatter<T, CharT>;
 
    basic_format_arg<basic_format_context> arg(size_t id) const noexcept;
    std::locale locale();
 
    iterator out();
    void advance_to(iterator it);
  };
}

[edit] Variable template std::format_kind

template<ranges::input_range R>
    requires same_as<R, remove_cvref_t<R>>
  constexpr range_format format_kind<R> = /* see description */;

[edit] Class template std::range_formatter

namespace std {
  template<class T, class CharT = char>
    requires same_as<remove_cvref_t<T>, T> && formattable<T, CharT>
  class range_formatter {
    formatter<T, CharT> underlying_;                        // exposition only
    basic_string_view<CharT> separator_ =                   // exposition only
      __STATICALLY_WIDEN<CharT>(", ");
    basic_string_view<CharT> __opening_bracket_ =           // exposition only
      __STATICALLY_WIDEN<CharT>("[");
    basic_string_view<CharT> __closing_bracket_ =           // exposition only
      __STATICALLY_WIDEN<CharT>("]");
 
  public:
    constexpr void set_separator(basic_string_view<CharT> sep);
    constexpr void set_brackets(basic_string_view<CharT> opening,
                                basic_string_view<CharT> closing);
    constexpr formatter<T, CharT>& underlying() { return underlying_; }
    constexpr const formatter<T, CharT>& underlying() const { return underlying_; }
 
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<ranges::input_range R, class FormatContext>
        requires formattable<ranges::range_reference_t<R>, CharT> &&
                 same_as<remove_cvref_t<ranges::range_reference_t<R>>, T>
      typename FormatContext::iterator
        format(R&& r, FormatContext& ctx) const;
  };
}

[edit] Class template __range_default_formatter

namespace std {
  template<ranges::input_range R, class CharT>
  struct __range_default_formatter<range_format::sequence, R, CharT> {
  private:
    using __maybe_const_r = __fmt_maybe_const<R, CharT>;
    range_formatter<remove_cvref_t<ranges::range_reference_t<__maybe_const_r>>,
                    CharT> underlying_;       // exposition only
 
  public:
    constexpr void set_separator(basic_string_view<CharT> sep);
    constexpr void set_brackets(basic_string_view<CharT> opening,
                                basic_string_view<CharT> closing);
 
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<class FormatContext>
      typename FormatContext::iterator
        format(__maybe_const_r& elems, FormatContext& ctx) const;
  };
}

[edit] Specialization of __range_default_formatter for maps

namespace std {
  template<ranges::input_range R, class CharT>
  struct __range_default_formatter<range_format::map, R, CharT> {
  private:
    using __maybe_const_map = __fmt_maybe_const<R, CharT>;          // exposition only
    using __element_type =                                          // exposition only
      remove_cvref_t<ranges::range_reference_t<__maybe_const_map>>;
    range_formatter<__element_type, CharT> underlying_;             // exposition only
  public:
    constexpr __range_default_formatter();
 
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<class FormatContext>
      typename FormatContext::iterator
        format(__maybe_const_map& r, FormatContext& ctx) const;
  };
}

[edit] Specialization of __range_default_formatter for sets

namespace std {
  template<ranges::input_range R, class CharT>
  struct __range_default_formatter<range_format::set, R, CharT> {
  private:
    using __maybe_const_set = __fmt_maybe_const<R, CharT>;          // exposition only
    range_formatter<remove_cvref_t<ranges::range_reference_t<__maybe_const_set>>,
                    CharT> underlying_;                             // exposition only
  public:
    constexpr __range_default_formatter();
 
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<class FormatContext>
      typename FormatContext::iterator
        format(__maybe_const_set& r, FormatContext& ctx) const;
  };
}

[edit] Specialization of __range_default_formatter for strings

namespace std {
  template<range_format K, ranges::input_range R, class CharT>
    requires (K == range_format::string || K == range_format::debug_string)
  struct __range_default_formatter<K, R, CharT> {
  private:
    formatter<basic_string<CharT>, CharT> underlying_;              // exposition only
 
  public:
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<class FormatContext>
      typename FormatContext::iterator
        format(/* see description */& str, FormatContext& ctx) const;
  };
}

[edit] Class template std::basic_format_arg

namespace std {
  template<class Context>
  class basic_format_arg {
  public:
    class handle;
 
  private:
    using char_type = typename Context::char_type;                     // exposition only
 
    variant<monostate, bool, char_type,
            int, unsigned int, long long int, unsigned long long int,
            float, double, long double,
            const char_type*, basic_string_view<char_type>,
            const void*, handle> value;                                // exposition only
 
    template<class T> explicit basic_format_arg(T&& v) noexcept;       // exposition only
    explicit basic_format_arg(float n) noexcept;                       // exposition only
    explicit basic_format_arg(double n) noexcept;                      // exposition only
    explicit basic_format_arg(long double n) noexcept;                 // exposition only
    explicit basic_format_arg(const char_type* s);                     // exposition only
 
    template<class traits>
      explicit basic_format_arg(
        basic_string_view<char_type, traits> s) noexcept;              // exposition only
 
    template<class traits, class Allocator>
      explicit basic_format_arg(
        const basic_string<char_type, traits, Allocator>& s) noexcept; // exposition only
 
    explicit basic_format_arg(nullptr_t) noexcept;                     // exposition only
 
    template<class T>
      explicit basic_format_arg(T* p) noexcept;                        // exposition only
 
  public:
    basic_format_arg() noexcept;
 
    explicit operator bool() const noexcept;
 
    template<class Visitor>
      decltype(auto) visit(this basic_format_arg arg, Visitor&& vis);
    template<class R, class Visitor>
      R visit(this basic_format_arg arg, Visitor&& vis);
  };
}

[edit] Class std::basic_format_arg::handle

namespace std {
  template<class Context>
  class basic_format_arg<Context>::handle {
    const void* ptr_;                                           // exposition only
    void (*format_)(basic_format_parse_context<char_type>&,
                    Context&, const void*);                     // exposition only
 
    template<class T> explicit handle(T&& val) noexcept;        // exposition only
 
    friend class basic_format_arg<Context>;                     // exposition only
 
  public:
    void format(basic_format_parse_context<char_type>&, Context& ctx) const;
  };
}

[edit] Class template __format_arg_store

namespace std {
  template<class Context, class... Args>
  class __format_arg_store {                                    // exposition only
    array<basic_format_arg<Context>, sizeof...(Args)> args;     // exposition only
  };
}

[edit] Class template std::basic_format_args

namespace std {
  template<class Context>
  class basic_format_args {
    size_t size_;                               // exposition only
    const basic_format_arg<Context>* data_;     // exposition only
 
  public:
    template<class... Args>
      basic_format_args(const __format_arg_store<Context, Args...>& store) noexcept;
 
    basic_format_arg<Context> get(size_t i) const noexcept;
  };
}

[edit] Tuple formatter

namespace std {
  template<class CharT, formattable<CharT>... Ts>
  struct formatter<__pair_or_tuple<Ts...>, CharT> {
  private:
    tuple<formatter<remove_cvref_t<Ts>, CharT>...> underlying_;     // exposition only
    basic_string_view<CharT> separator_ =                           // exposition only
      __STATICALLY_WIDEN<CharT>(", ");
    basic_string_view<CharT> opening_bracket_ =                     // exposition only
      __STATICALLY_WIDEN<CharT>("(");
    basic_string_view<CharT> closing_bracket_ =                     // exposition only
      __STATICALLY_WIDEN<CharT>(")");
 
  public:
    constexpr void set_separator(basic_string_view<CharT> sep);
    constexpr void set_brackets(basic_string_view<CharT> opening,
                                basic_string_view<CharT> closing);
 
    template<class ParseContext>
      constexpr typename ParseContext::iterator
        parse(ParseContext& ctx);
 
    template<class FormatContext>
      typename FormatContext::iterator
        format(/* see description */& elems, FormatContext& ctx) const;
  };
}

[edit] Class std::format_error

namespace std {
  class format_error : public runtime_error {
  public:
    explicit format_error(const string& what_arg);
    explicit format_error(const char* what_arg);
  };
}
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