text: // Formatting library for C++ - the core API
  //
  // Copyright (c) 2012 - present, Victor Zverovich
  // All rights reserved.
  //
  // For the license information refer to format.h.
  
  #ifndef FMT_CORE_H_
  #define FMT_CORE_H_
  
  #include <cstdio>  // std::FILE
  #include <cstring>
  #include <iterator>
  #include <string>
  #include <type_traits>
  
  // The fmt library version in the form major * 10000 + minor * 100 + patch.
  #define FMT_VERSION 60103
  
  #ifdef __has_feature
  #  define FMT_HAS_FEATURE(x) __has_feature(x)
  #else
  #  define FMT_HAS_FEATURE(x) 0
  #endif
  
  #if defined(__has_include) && !defined(__INTELLISENSE__) && \
      !(defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1600)
  #  define FMT_HAS_INCLUDE(x) __has_include(x)
  #else
  #  define FMT_HAS_INCLUDE(x) 0
  #endif
  
  #ifdef __has_cpp_attribute
  #  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
  #else
  #  define FMT_HAS_CPP_ATTRIBUTE(x) 0
  #endif
  
  #if defined(__GNUC__) && !defined(__clang__)
  #  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
  #else
  #  define FMT_GCC_VERSION 0
  #endif
  
  #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
  #  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
  #else
  #  define FMT_HAS_GXX_CXX11 0
  #endif
  
  #ifdef __NVCC__
  #  define FMT_NVCC __NVCC__
  #else
  #  define FMT_NVCC 0
  #endif
  
  #ifdef _MSC_VER
  #  define FMT_MSC_VER _MSC_VER
  #else
  #  define FMT_MSC_VER 0
  #endif
  
  // Check if relaxed C++14 constexpr is supported.
  // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
  #ifndef FMT_USE_CONSTEXPR
  #  define FMT_USE_CONSTEXPR                                           \
      (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
       (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
          !FMT_NVCC
  #endif
  #if FMT_USE_CONSTEXPR
  #  define FMT_CONSTEXPR constexpr
  #  define FMT_CONSTEXPR_DECL constexpr
  #else
  #  define FMT_CONSTEXPR inline
  #  define FMT_CONSTEXPR_DECL
  #endif
  
  #ifndef FMT_OVERRIDE
  #  if FMT_HAS_FEATURE(cxx_override) || \
        (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
  #    define FMT_OVERRIDE override
  #  else
  #    define FMT_OVERRIDE
  #  endif
  #endif
  
  // Check if exceptions are disabled.
  #ifndef FMT_EXCEPTIONS
  #  if (defined(__GNUC__) && !defined(__EXCEPTIONS)) || \
        FMT_MSC_VER && !_HAS_EXCEPTIONS
  #    define FMT_EXCEPTIONS 0
  #  else
  #    define FMT_EXCEPTIONS 1
  #  endif
  #endif
  
  // Define FMT_USE_NOEXCEPT to make fmt use noexcept (C++11 feature).
  #ifndef FMT_USE_NOEXCEPT
  #  define FMT_USE_NOEXCEPT 0
  #endif
  
  #if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
      (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
  #  define FMT_DETECTED_NOEXCEPT noexcept
  #  define FMT_HAS_CXX11_NOEXCEPT 1
  #else
  #  define FMT_DETECTED_NOEXCEPT throw()
  #  define FMT_HAS_CXX11_NOEXCEPT 0
  #endif
  
  #ifndef FMT_NOEXCEPT
  #  if FMT_EXCEPTIONS || FMT_HAS_CXX11_NOEXCEPT
  #    define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
  #  else
  #    define FMT_NOEXCEPT
  #  endif
  #endif
  
  // [[noreturn]] is disabled on MSVC and NVCC because of bogus unreachable code
  // warnings.
  #if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER && \
      !FMT_NVCC
  #  define FMT_NORETURN [[noreturn]]
  #else
  #  define FMT_NORETURN
  #endif
  
  #ifndef FMT_DEPRECATED
  #  if (FMT_HAS_CPP_ATTRIBUTE(deprecated) && __cplusplus >= 201402L) || \
        FMT_MSC_VER >= 1900
  #    define FMT_DEPRECATED [[deprecated]]
  #  else
  #    if defined(__GNUC__) || defined(__clang__)
  #      define FMT_DEPRECATED __attribute__((deprecated))
  #    elif FMT_MSC_VER
  #      define FMT_DEPRECATED __declspec(deprecated)
  #    else
  #      define FMT_DEPRECATED /* deprecated */
  #    endif
  #  endif
  #endif
  
  // Workaround broken [[deprecated]] in the Intel compiler and NVCC.
  #if defined(__INTEL_COMPILER) || FMT_NVCC
  #  define FMT_DEPRECATED_ALIAS
  #else
  #  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
  #endif
  
  #ifndef FMT_BEGIN_NAMESPACE
  #  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
        FMT_MSC_VER >= 1900
  #    define FMT_INLINE_NAMESPACE inline namespace
  #    define FMT_END_NAMESPACE \
        }                       \
        }
  #  else
  #    define FMT_INLINE_NAMESPACE namespace
  #    define FMT_END_NAMESPACE \
        }                       \
        using namespace v6;     \
        }
  #  endif
  #  define FMT_BEGIN_NAMESPACE \
      namespace fmt {           \
      FMT_INLINE_NAMESPACE v6 {
  #endif
  
  #if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
  #  if FMT_MSC_VER
  #    define FMT_NO_W4275 __pragma(warning(suppress : 4275))
  #  else
  #    define FMT_NO_W4275
  #  endif
  #  define FMT_CLASS_API FMT_NO_W4275
  #  ifdef FMT_EXPORT
  #    define FMT_API __declspec(dllexport)
  #  elif defined(FMT_SHARED)
  #    define FMT_API __declspec(dllimport)
  #    define FMT_EXTERN_TEMPLATE_API FMT_API
  #  endif
  #endif
  #ifndef FMT_CLASS_API
  #  define FMT_CLASS_API
  #endif
  #ifndef FMT_API
  #  if FMT_GCC_VERSION || FMT_CLANG_VERSION
  #    define FMT_API __attribute__((visibility("default")))
  #    define FMT_EXTERN_TEMPLATE_API FMT_API
  #    define FMT_INSTANTIATION_DEF_API
  #  else
  #    define FMT_API
  #  endif
  #endif
  #ifndef FMT_EXTERN_TEMPLATE_API
  #  define FMT_EXTERN_TEMPLATE_API
  #endif
  #ifndef FMT_INSTANTIATION_DEF_API
  #  define FMT_INSTANTIATION_DEF_API FMT_API
  #endif
  
  #ifndef FMT_HEADER_ONLY
  #  define FMT_EXTERN extern
  #else
  #  define FMT_EXTERN
  #endif
  
  // libc++ supports string_view in pre-c++17.
  #if (FMT_HAS_INCLUDE(<string_view>) &&                       \
       (__cplusplus > 201402L || defined(_LIBCPP_VERSION))) || \
      (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
  #  include <string_view>
  #  define FMT_USE_STRING_VIEW
  #elif FMT_HAS_INCLUDE("experimental/string_view") && __cplusplus >= 201402L
  #  include <experimental/string_view>
  #  define FMT_USE_EXPERIMENTAL_STRING_VIEW
  #endif
  
  #ifndef FMT_UNICODE
  #  define FMT_UNICODE 0
  #endif
  #if FMT_UNICODE
  #  pragma execution_character_set("utf-8")
  #endif
  
  FMT_BEGIN_NAMESPACE
  
  // Implementations of enable_if_t and other metafunctions for older systems.
  template <bool B, class T = void>
  using enable_if_t = typename std::enable_if<B, T>::type;
  template <bool B, class T, class F>
  using conditional_t = typename std::conditional<B, T, F>::type;
  template <bool B> using bool_constant = std::integral_constant<bool, B>;
  template <typename T>
  using remove_reference_t = typename std::remove_reference<T>::type;
  template <typename T>
  using remove_const_t = typename std::remove_const<T>::type;
  template <typename T>
  using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
  template <typename T> struct type_identity { using type = T; };
  template <typename T> using type_identity_t = typename type_identity<T>::type;
  
  struct monostate {};
  
  // An enable_if helper to be used in template parameters which results in much
  // shorter symbols: https://godbolt.org/z/sWw4vP. Extra parentheses are needed
  // to workaround a bug in MSVC 2019 (see #1140 and #1186).
  #define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
  
  namespace internal {
  
  // A workaround for gcc 4.8 to make void_t work in a SFINAE context.
  template <typename... Ts> struct void_t_impl { using type = void; };
  
  FMT_API void assert_fail(const char* file, int line, const char* message);
  
  #ifndef FMT_ASSERT
  #  ifdef NDEBUG
  #    define FMT_ASSERT(condition, message)
  #  else
  #    define FMT_ASSERT(condition, message) \
        ((condition)                         \
             ? void()                        \
             : ::fmt::internal::assert_fail(__FILE__, __LINE__, (message)))
  #  endif
  #endif
  
  #if defined(FMT_USE_STRING_VIEW)
  template <typename Char> using std_string_view = std::basic_string_view<Char>;
  #elif defined(FMT_USE_EXPERIMENTAL_STRING_VIEW)
  template <typename Char>
  using std_string_view = std::experimental::basic_string_view<Char>;
  #else
  template <typename T> struct std_string_view {};
  #endif
  
  #ifdef FMT_USE_INT128
  // Do nothing.
  #elif defined(__SIZEOF_INT128__) && !FMT_NVCC
  #  define FMT_USE_INT128 1
  using int128_t = __int128_t;
  using uint128_t = __uint128_t;
  #else
  #  define FMT_USE_INT128 0
  #endif
  #if !FMT_USE_INT128
  struct int128_t {};
  struct uint128_t {};
  #endif
  
  // Casts a nonnegative integer to unsigned.
  template <typename Int>
  FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
    FMT_ASSERT(value >= 0, "negative value");
    return static_cast<typename std::make_unsigned<Int>::type>(value);
  }
  }  // namespace internal
  
  template <typename... Ts>
  using void_t = typename internal::void_t_impl<Ts...>::type;
  
  /**
    An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
    subset of the API. ``fmt::basic_string_view`` is used for format strings even
    if ``std::string_view`` is available to prevent issues when a library is
    compiled with a different ``-std`` option than the client code (which is not
    recommended).
   */
  template <typename Char> class basic_string_view {
   private:
    const Char* data_;
    size_t size_;
  
   public:
    using char_type FMT_DEPRECATED_ALIAS = Char;
    using value_type = Char;
    using iterator = const Char*;
  
    FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
  
    /** Constructs a string reference object from a C string and a size. */
    FMT_CONSTEXPR basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
        : data_(s),
          size_(count) {}
  
    /**
      \rst
      Constructs a string reference object from a C string computing
      the size with ``std::char_traits<Char>::length``.
      \endrst
     */
    basic_string_view(const Char* s)
        : data_(s), size_(std::char_traits<Char>::length(s)) {}
  
    /** Constructs a string reference from a ``std::basic_string`` object. */
    template <typename Traits, typename Alloc>
    FMT_CONSTEXPR basic_string_view(
        const std::basic_string<Char, Traits, Alloc>& s) FMT_NOEXCEPT
        : data_(s.data()),
          size_(s.size()) {}
  
    template <
        typename S,
        FMT_ENABLE_IF(std::is_same<S, internal::std_string_view<Char>>::value)>
    FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
                                                        size_(s.size()) {}
  
    /** Returns a pointer to the string data. */
    FMT_CONSTEXPR const Char* data() const { return data_; }
  
    /** Returns the string size. */
    FMT_CONSTEXPR size_t size() const { return size_; }
  
    FMT_CONSTEXPR iterator begin() const { return data_; }
    FMT_CONSTEXPR iterator end() const { return data_ + size_; }
  
    FMT_CONSTEXPR const Char& operator[](size_t pos) const { return data_[pos]; }
  
    FMT_CONSTEXPR void remove_prefix(size_t n) {
      data_ += n;
      size_ -= n;
    }
  
    // Lexicographically compare this string reference to other.
    int compare(basic_string_view other) const {
      size_t str_size = size_ < other.size_ ? size_ : other.size_;
      int result = std::char_traits<Char>::compare(data_, other.data_, str_size);
      if (result == 0)
        result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
      return result;
    }
  
    friend bool operator==(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) == 0;
    }
    friend bool operator!=(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) != 0;
    }
    friend bool operator<(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) < 0;
    }
    friend bool operator<=(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) <= 0;
    }
    friend bool operator>(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) > 0;
    }
    friend bool operator>=(basic_string_view lhs, basic_string_view rhs) {
      return lhs.compare(rhs) >= 0;
    }
  };
  
  using string_view = basic_string_view<char>;
  using wstring_view = basic_string_view<wchar_t>;
  
  #ifndef __cpp_char8_t
  // A UTF-8 code unit type.
  enum char8_t : unsigned char {};
  #endif
  
  /** Specifies if ``T`` is a character type. Can be specialized by users. */
  template <typename T> struct is_char : std::false_type {};
  template <> struct is_char<char> : std::true_type {};
  template <> struct is_char<wchar_t> : std::true_type {};
  template <> struct is_char<char8_t> : std::true_type {};
  template <> struct is_char<char16_t> : std::true_type {};
  template <> struct is_char<char32_t> : std::true_type {};
  
  /**
    \rst
    Returns a string view of `s`. In order to add custom string type support to
    {fmt} provide an overload of `to_string_view` for it in the same namespace as
    the type for the argument-dependent lookup to work.
  
    **Example**::
  
      namespace my_ns {
      inline string_view to_string_view(const my_string& s) {
        return {s.data(), s.length()};
      }
      }
      std::string message = fmt::format(my_string("The answer is {}"), 42);
    \endrst
   */
  template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
  inline basic_string_view<Char> to_string_view(const Char* s) {
    return s;
  }
  
  template <typename Char, typename Traits, typename Alloc>
  inline basic_string_view<Char> to_string_view(
      const std::basic_string<Char, Traits, Alloc>& s) {
    return s;
  }
  
  template <typename Char>
  inline basic_string_view<Char> to_string_view(basic_string_view<Char> s) {
    return s;
  }
  
  template <typename Char,
            FMT_ENABLE_IF(!std::is_empty<internal::std_string_view<Char>>::value)>
  inline basic_string_view<Char> to_string_view(
      internal::std_string_view<Char> s) {
    return s;
  }
  
  // A base class for compile-time strings. It is defined in the fmt namespace to
  // make formatting functions visible via ADL, e.g. format(fmt("{}"), 42).
  struct compile_string {};
  
  template <typename S>
  struct is_compile_string : std::is_base_of<compile_string, S> {};
  
  template <typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
  constexpr basic_string_view<typename S::char_type> to_string_view(const S& s) {
    return s;
  }
  
  namespace internal {
  void to_string_view(...);
  using fmt::v6::to_string_view;
  
  // Specifies whether S is a string type convertible to fmt::basic_string_view.
  // It should be a constexpr function but MSVC 2017 fails to compile it in
  // enable_if and MSVC 2015 fails to compile it as an alias template.
  template <typename S>
  struct is_string : std::is_class<decltype(to_string_view(std::declval<S>()))> {
  };
  
  template <typename S, typename = void> struct char_t_impl {};
  template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
    using result = decltype(to_string_view(std::declval<S>()));
    using type = typename result::value_type;
  };
  
  struct error_handler {
    FMT_CONSTEXPR error_handler() = default;
    FMT_CONSTEXPR error_handler(const error_handler&) = default;
  
    // This function is intentionally not constexpr to give a compile-time error.
    FMT_NORETURN FMT_API void on_error(const char* message);
  };
  }  // namespace internal
  
  /** String's character type. */
  template <typename S> using char_t = typename internal::char_t_impl<S>::type;
  
  /**
    \rst
    Parsing context consisting of a format string range being parsed and an
    argument counter for automatic indexing.
  
    You can use one of the following type aliases for common character types:
  
    +-----------------------+-------------------------------------+
    | Type                  | Definition                          |
    +=======================+=====================================+
    | format_parse_context  | basic_format_parse_context<char>    |
    +-----------------------+-------------------------------------+
    | wformat_parse_context | basic_format_parse_context<wchar_t> |
    +-----------------------+-------------------------------------+
    \endrst
   */
  template <typename Char, typename ErrorHandler = internal::error_handler>
  class basic_format_parse_context : private ErrorHandler {
   private:
    basic_string_view<Char> format_str_;
    int next_arg_id_;
  
   public:
    using char_type = Char;
    using iterator = typename basic_string_view<Char>::iterator;
  
    explicit FMT_CONSTEXPR basic_format_parse_context(
        basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
        : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
  
    /**
      Returns an iterator to the beginning of the format string range being
      parsed.
     */
    FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
      return format_str_.begin();
    }
  
    /**
      Returns an iterator past the end of the format string range being parsed.
     */
    FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
  
    /** Advances the begin iterator to ``it``. */
    FMT_CONSTEXPR void advance_to(iterator it) {
      format_str_.remove_prefix(internal::to_unsigned(it - begin()));
    }
  
    /**
      Reports an error if using the manual argument indexing; otherwise returns
      the next argument index and switches to the automatic indexing.
     */
    FMT_CONSTEXPR int next_arg_id() {
      if (next_arg_id_ >= 0) return next_arg_id_++;
      on_error("cannot switch from manual to automatic argument indexing");
      return 0;
    }
  
    /**
      Reports an error if using the automatic argument indexing; otherwise
      switches to the manual indexing.
     */
    FMT_CONSTEXPR void check_arg_id(int) {
      if (next_arg_id_ > 0)
        on_error("cannot switch from automatic to manual argument indexing");
      else
        next_arg_id_ = -1;
    }
  
    FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {}
  
    FMT_CONSTEXPR void on_error(const char* message) {
      ErrorHandler::on_error(message);
    }
  
    FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
  };
  
  using format_parse_context = basic_format_parse_context<char>;
  using wformat_parse_context = basic_format_parse_context<wchar_t>;
  
  template <typename Char, typename ErrorHandler = internal::error_handler>
  using basic_parse_context FMT_DEPRECATED_ALIAS =
      basic_format_parse_context<Char, ErrorHandler>;
  using parse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<char>;
  using wparse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<wchar_t>;
  
  template <typename Context> class basic_format_arg;
  template <typename Context> class basic_format_args;
  
  // A formatter for objects of type T.
  template <typename T, typename Char = char, typename Enable = void>
  struct formatter {
    // A deleted default constructor indicates a disabled formatter.
    formatter() = delete;
  };
  
  template <typename T, typename Char, typename Enable = void>
  struct FMT_DEPRECATED convert_to_int
      : bool_constant<!std::is_arithmetic<T>::value &&
                      std::is_convertible<T, int>::value> {};
  
  // Specifies if T has an enabled formatter specialization. A type can be
  // formattable even if it doesn't have a formatter e.g. via a conversion.
  template <typename T, typename Context>
  using has_formatter =
      std::is_constructible<typename Context::template formatter_type<T>>;
  
  namespace internal {
  
  /** A contiguous memory buffer with an optional growing ability. */
  template <typename T> class buffer {
   private:
    T* ptr_;
    std::size_t size_;
    std::size_t capacity_;
  
   protected:
    // Don't initialize ptr_ since it is not accessed to save a few cycles.
    buffer(std::size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
  
    buffer(T* p = nullptr, std::size_t sz = 0, std::size_t cap = 0) FMT_NOEXCEPT
        : ptr_(p),
          size_(sz),
          capacity_(cap) {}
  
    /** Sets the buffer data and capacity. */
    void set(T* buf_data, std::size_t buf_capacity) FMT_NOEXCEPT {
      ptr_ = buf_data;
      capacity_ = buf_capacity;
    }
  
    /** Increases the buffer capacity to hold at least *capacity* elements. */
    virtual void grow(std::size_t capacity) = 0;
  
   public:
    using value_type = T;
    using const_reference = const T&;
  
    buffer(const buffer&) = delete;
    void operator=(const buffer&) = delete;
    virtual ~buffer() = default;
  
    T* begin() FMT_NOEXCEPT { return ptr_; }
    T* end() FMT_NOEXCEPT { return ptr_ + size_; }
  
    /** Returns the size of this buffer. */
    std::size_t size() const FMT_NOEXCEPT { return size_; }
  
    /** Returns the capacity of this buffer. */
    std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }
  
    /** Returns a pointer to the buffer data. */
    T* data() FMT_NOEXCEPT { return ptr_; }
  
    /** Returns a pointer to the buffer data. */
    const T* data() const FMT_NOEXCEPT { return ptr_; }
  
    /**
      Resizes the buffer. If T is a POD type new elements may not be initialized.
     */
    void resize(std::size_t new_size) {
      reserve(new_size);
      size_ = new_size;
    }
  
    /** Clears this buffer. */
    void clear() { size_ = 0; }
  
    /** Reserves space to store at least *capacity* elements. */
    void reserve(std::size_t new_capacity) {
      if (new_capacity > capacity_) grow(new_capacity);
    }
  
    void push_back(const T& value) {
      reserve(size_ + 1);
      ptr_[size_++] = value;
    }
  
    /** Appends data to the end of the buffer. */
    template <typename U> void append(const U* begin, const U* end);
  
    T& operator[](std::size_t index) { return ptr_[index]; }
    const T& operator[](std::size_t index) const { return ptr_[index]; }
  };
  
  // A container-backed buffer.
  template <typename Container>
  class container_buffer : public buffer<typename Container::value_type> {
   private:
    Container& container_;
  
   protected:
    void grow(std::size_t capacity) FMT_OVERRIDE {
      container_.resize(capacity);
      this->set(&container_[0], capacity);
    }
  
   public:
    explicit container_buffer(Container& c)
        : buffer<typename Container::value_type>(c.size()), container_(c) {}
  };
  
  // Extracts a reference to the container from back_insert_iterator.
  template <typename Container>
  inline Container& get_container(std::back_insert_iterator<Container> it) {
    using bi_iterator = std::back_insert_iterator<Container>;
    struct accessor : bi_iterator {
      accessor(bi_iterator iter) : bi_iterator(iter) {}
      using bi_iterator::container;
    };
    return *accessor(it).container;
  }
  
  template <typename T, typename Char = char, typename Enable = void>
  struct fallback_formatter {
    fallback_formatter() = delete;
  };
  
  // Specifies if T has an enabled fallback_formatter specialization.
  template <typename T, typename Context>
  using has_fallback_formatter =
      std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
  
  template <typename Char> struct named_arg_base;
  template <typename T, typename Char> struct named_arg;
  
  enum class type {
    none_type,
    named_arg_type,
    // Integer types should go first,
    int_type,
    uint_type,
    long_long_type,
    ulong_long_type,
    int128_type,
    uint128_type,
    bool_type,
    char_type,
    last_integer_type = char_type,
    // followed by floating-point types.
    float_type,
    double_type,
    long_double_type,
    last_numeric_type = long_double_type,
    cstring_type,
    string_type,
    pointer_type,
    custom_type
  };
  
  // Maps core type T to the corresponding type enum constant.
  template <typename T, typename Char>
  struct type_constant : std::integral_constant<type, type::custom_type> {};
  
  #define FMT_TYPE_CONSTANT(Type, constant) \
    template <typename Char>                \
    struct type_constant<Type, Char>        \
        : std::integral_constant<type, type::constant> {}
  
  FMT_TYPE_CONSTANT(const named_arg_base<Char>&, named_arg_type);
  FMT_TYPE_CONSTANT(int, int_type);
  FMT_TYPE_CONSTANT(unsigned, uint_type);
  FMT_TYPE_CONSTANT(long long, long_long_type);
  FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
  FMT_TYPE_CONSTANT(int128_t, int128_type);
  FMT_TYPE_CONSTANT(uint128_t, uint128_type);
  FMT_TYPE_CONSTANT(bool, bool_type);
  FMT_TYPE_CONSTANT(Char, char_type);
  FMT_TYPE_CONSTANT(float, float_type);
  FMT_TYPE_CONSTANT(double, double_type);
  FMT_TYPE_CONSTANT(long double, long_double_type);
  FMT_TYPE_CONSTANT(const Char*, cstring_type);
  FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
  FMT_TYPE_CONSTANT(const void*, pointer_type);
  
  FMT_CONSTEXPR bool is_integral_type(type t) {
    FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
    return t > type::none_type && t <= type::last_integer_type;
  }
  
  FMT_CONSTEXPR bool is_arithmetic_type(type t) {
    FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
    return t > type::none_type && t <= type::last_numeric_type;
  }
  
  template <typename Char> struct string_value {
    const Char* data;
    std::size_t size;
  };
  
  template <typename Context> struct custom_value {
    using parse_context = basic_format_parse_context<typename Context::char_type>;
    const void* value;
    void (*format)(const void* arg, parse_context& parse_ctx, Context& ctx);
  };
  
  // A formatting argument value.
  template <typename Context> class value {
   public:
    using char_type = typename Context::char_type;
  
    union {
      int int_value;
      unsigned uint_value;
      long long long_long_value;
      unsigned long long ulong_long_value;
      int128_t int128_value;
      uint128_t uint128_value;
      bool bool_value;
      char_type char_value;
      float float_value;
      double double_value;
      long double long_double_value;
      const void* pointer;
      string_value<char_type> string;
      custom_value<Context> custom;
      const named_arg_base<char_type>* named_arg;
    };
  
    FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
    FMT_CONSTEXPR value(unsigned val) : uint_value(val) {}
    value(long long val) : long_long_value(val) {}
    value(unsigned long long val) : ulong_long_value(val) {}
    value(int128_t val) : int128_value(val) {}
    value(uint128_t val) : uint128_value(val) {}
    value(float val) : float_value(val) {}
    value(double val) : double_value(val) {}
    value(long double val) : long_double_value(val) {}
    value(bool val) : bool_value(val) {}
    value(char_type val) : char_value(val) {}
    value(const char_type* val) { string.data = val; }
    value(basic_string_view<char_type> val) {
      string.data = val.data();
      string.size = val.size();
    }
    value(const void* val) : pointer(val) {}
  
    template <typename T> value(const T& val) {
      custom.value = &val;
      // Get the formatter type through the context to allow different contexts
      // have different extension points, e.g. `formatter<T>` for `format` and
      // `printf_formatter<T>` for `printf`.
      custom.format = format_custom_arg<
          T, conditional_t<has_formatter<T, Context>::value,
                           typename Context::template formatter_type<T>,
                           fallback_formatter<T, char_type>>>;
    }
  
    value(const named_arg_base<char_type>& val) { named_arg = &val; }
  
   private:
    // Formats an argument of a custom type, such as a user-defined class.
    template <typename T, typename Formatter>
    static void format_custom_arg(
        const void* arg, basic_format_parse_context<char_type>& parse_ctx,
        Context& ctx) {
      Formatter f;
      parse_ctx.advance_to(f.parse(parse_ctx));
      ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
    }
  };
  
  template <typename Context, typename T>
  FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value);
  
  // To minimize the number of types we need to deal with, long is translated
  // either to int or to long long depending on its size.
  enum { long_short = sizeof(long) == sizeof(int) };
  using long_type = conditional_t<long_short, int, long long>;
  using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
  
  // Maps formatting arguments to core types.
  template <typename Context> struct arg_mapper {
    using char_type = typename Context::char_type;
  
    FMT_CONSTEXPR int map(signed char val) { return val; }
    FMT_CONSTEXPR unsigned map(unsigned char val) { return val; }
    FMT_CONSTEXPR int map(short val) { return val; }
    FMT_CONSTEXPR unsigned map(unsigned short val) { return val; }
    FMT_CONSTEXPR int map(int val) { return val; }
    FMT_CONSTEXPR unsigned map(unsigned val) { return val; }
    FMT_CONSTEXPR long_type map(long val) { return val; }
    FMT_CONSTEXPR ulong_type map(unsigned long val) { return val; }
    FMT_CONSTEXPR long long map(long long val) { return val; }
    FMT_CONSTEXPR unsigned long long map(unsigned long long val) { return val; }
    FMT_CONSTEXPR int128_t map(int128_t val) { return val; }
    FMT_CONSTEXPR uint128_t map(uint128_t val) { return val; }
    FMT_CONSTEXPR bool map(bool val) { return val; }
  
    template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
    FMT_CONSTEXPR char_type map(T val) {
      static_assert(
          std::is_same<T, char>::value || std::is_same<T, char_type>::value,
          "mixing character types is disallowed");
      return val;
    }
  
    FMT_CONSTEXPR float map(float val) { return val; }
    FMT_CONSTEXPR double map(double val) { return val; }
    FMT_CONSTEXPR long double map(long double val) { return val; }
  
    FMT_CONSTEXPR const char_type* map(char_type* val) { return val; }
    FMT_CONSTEXPR const char_type* map(const char_type* val) { return val; }
    template <typename T, FMT_ENABLE_IF(is_string<T>::value)>
    FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
      static_assert(std::is_same<char_type, char_t<T>>::value,
                    "mixing character types is disallowed");
      return to_string_view(val);
    }
    template <typename T,
              FMT_ENABLE_IF(
                  std::is_constructible<basic_string_view<char_type>, T>::value &&
                  !is_string<T>::value && !has_formatter<T, Context>::value &&
                  !has_fallback_formatter<T, Context>::value)>
    FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
      return basic_string_view<char_type>(val);
    }
    template <
        typename T,
        FMT_ENABLE_IF(
            std::is_constructible<std_string_view<char_type>, T>::value &&
            !std::is_constructible<basic_string_view<char_type>, T>::value &&
            !is_string<T>::value && !has_formatter<T, Context>::value &&
            !has_fallback_formatter<T, Context>::value)>
    FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
      return std_string_view<char_type>(val);
    }
    FMT_CONSTEXPR const char* map(const signed char* val) {
      static_assert(std::is_same<char_type, char>::value, "invalid string type");
      return reinterpret_cast<const char*>(val);
    }
    FMT_CONSTEXPR const char* map(const unsigned char* val) {
      static_assert(std::is_same<char_type, char>::value, "invalid string type");
      return reinterpret_cast<const char*>(val);
    }
  
    FMT_CONSTEXPR const void* map(void* val) { return val; }
    FMT_CONSTEXPR const void* map(const void* val) { return val; }
    FMT_CONSTEXPR const void* map(std::nullptr_t val) { return val; }
    template <typename T> FMT_CONSTEXPR int map(const T*) {
      // Formatting of arbitrary pointers is disallowed. If you want to output
      // a pointer cast it to "void *" or "const void *". In particular, this
      // forbids formatting of "[const] volatile char *" which is printed as bool
      // by iostreams.
      static_assert(!sizeof(T), "formatting of non-void pointers is disallowed");
      return 0;
    }
  
    template <typename T,
              FMT_ENABLE_IF(std::is_enum<T>::value &&
                            !has_formatter<T, Context>::value &&
                            !has_fallback_formatter<T, Context>::value)>
    FMT_CONSTEXPR auto map(const T& val) -> decltype(
        map(static_cast<typename std::underlying_type<T>::type>(val))) {
      return map(static_cast<typename std::underlying_type<T>::type>(val));
    }
    template <
        typename T,
        FMT_ENABLE_IF(
            !is_string<T>::value && !is_char<T>::value &&
            (has_formatter<T, Context>::value ||
             has_fallback_formatter<T, Context>::value))>
    FMT_CONSTEXPR const T& map(const T& val) {
      return val;
    }
  
    template <typename T>
    FMT_CONSTEXPR const named_arg_base<char_type>& map(
        const named_arg<T, char_type>& val) {
      auto arg = make_arg<Context>(val.value);
      std::memcpy(val.data, &arg, sizeof(arg));
      return val;
    }
  
    int map(...) {
      constexpr bool formattable = sizeof(Context) == 0;
      static_assert(
          formattable,
          "Cannot format argument. To make type T formattable provide a "
          "formatter<T> specialization: "
          "https://fmt.dev/latest/api.html#formatting-user-defined-types");
      return 0;
    }
  };
  
  // A type constant after applying arg_mapper<Context>.
  template <typename T, typename Context>
  using mapped_type_constant =
      type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
                    typename Context::char_type>;
  
  enum { packed_arg_bits = 5 };
  // Maximum number of arguments with packed types.
  enum { max_packed_args = 63 / packed_arg_bits };
  enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
  
  template <typename Context> class arg_map;
  }  // namespace internal
  
  // A formatting argument. It is a trivially copyable/constructible type to
  // allow storage in basic_memory_buffer.
  template <typename Context> class basic_format_arg {
   private:
    internal::value<Context> value_;
    internal::type type_;
  
    template <typename ContextType, typename T>
    friend FMT_CONSTEXPR basic_format_arg<ContextType> internal::make_arg(
        const T& value);
  
    template <typename Visitor, typename Ctx>
    friend FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
                                               const basic_format_arg<Ctx>& arg)
        -> decltype(vis(0));
  
    friend class basic_format_args<Context>;
    friend class internal::arg_map<Context>;
  
    using char_type = typename Context::char_type;
  
   public:
    class handle {
     public:
      explicit handle(internal::custom_value<Context> custom) : custom_(custom) {}
  
      void format(basic_format_parse_context<char_type>& parse_ctx,
                  Context& ctx) const {
        custom_.format(custom_.value, parse_ctx, ctx);
      }
  
     private:
      internal::custom_value<Context> custom_;
    };
  
    FMT_CONSTEXPR basic_format_arg() : type_(internal::type::none_type) {}
  
    FMT_CONSTEXPR explicit operator bool() const FMT_NOEXCEPT {
      return type_ != internal::type::none_type;
    }
  
    internal::type type() const { return type_; }
  
    bool is_integral() const { return internal::is_integral_type(type_); }
    bool is_arithmetic() const { return internal::is_arithmetic_type(type_); }
  };
  
  /**
    \rst
    Visits an argument dispatching to the appropriate visit method based on
    the argument type. For example, if the argument type is ``double`` then
    ``vis(value)`` will be called with the value of type ``double``.
    \endrst
   */
  template <typename Visitor, typename Context>
  FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
                                      const basic_format_arg<Context>& arg)
      -> decltype(vis(0)) {
    using char_type = typename Context::char_type;
    switch (arg.type_) {
    case internal::type::none_type:
      break;
    case internal::type::named_arg_type:
      FMT_ASSERT(false, "invalid argument type");
      break;
    case internal::type::int_type:
      return vis(arg.value_.int_value);
    case internal::type::uint_type:
      return vis(arg.value_.uint_value);
    case internal::type::long_long_type:
      return vis(arg.value_.long_long_value);
    case internal::type::ulong_long_type:
      return vis(arg.value_.ulong_long_value);
  #if FMT_USE_INT128
    case internal::type::int128_type:
      return vis(arg.value_.int128_value);
    case internal::type::uint128_type:
      return vis(arg.value_.uint128_value);
  #else
    case internal::type::int128_type:
    case internal::type::uint128_type:
      break;
  #endif
    case internal::type::bool_type:
      return vis(arg.value_.bool_value);
    case internal::type::char_type:
      return vis(arg.value_.char_value);
    case internal::type::float_type:
      return vis(arg.value_.float_value);
    case internal::type::double_type:
      return vis(arg.value_.double_value);
    case internal::type::long_double_type:
      return vis(arg.value_.long_double_value);
    case internal::type::cstring_type:
      return vis(arg.value_.string.data);
    case internal::type::string_type:
      return vis(basic_string_view<char_type>(arg.value_.string.data,
                                              arg.value_.string.size));
    case internal::type::pointer_type:
      return vis(arg.value_.pointer);
    case internal::type::custom_type:
      return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
    }
    return vis(monostate());
  }
  
  namespace internal {
  // A map from argument names to their values for named arguments.
  template <typename Context> class arg_map {
   private:
    using char_type = typename Context::char_type;
  
    struct entry {
      basic_string_view<char_type> name;
      basic_format_arg<Context> arg;
    };
  
    entry* map_;
    unsigned size_;
  
    void push_back(value<Context> val) {
      const auto& named = *val.named_arg;
      map_[size_] = {named.name, named.template deserialize<Context>()};
      ++size_;
    }
  
   public:
    arg_map(const arg_map&) = delete;
    void operator=(const arg_map&) = delete;
    arg_map() : map_(nullptr), size_(0) {}
    void init(const basic_format_args<Context>& args);
    ~arg_map() { delete[] map_; }
  
    basic_format_arg<Context> find(basic_string_view<char_type> name) const {
      // The list is unsorted, so just return the first matching name.
      for (entry *it = map_, *end = map_ + size_; it != end; ++it) {
        if (it->name == name) return it->arg;
      }
      return {};
    }
  };
  
  // A type-erased reference to an std::locale to avoid heavy <locale> include.
  class locale_ref {
   private:
    const void* locale_;  // A type-erased pointer to std::locale.
  
   public:
    locale_ref() : locale_(nullptr) {}
    template <typename Locale> explicit locale_ref(const Locale& loc);
  
    explicit operator bool() const FMT_NOEXCEPT { return locale_ != nullptr; }
  
    template <typename Locale> Locale get() const;
  };
  
  template <typename> constexpr unsigned long long encode_types() { return 0; }
  
  template <typename Context, typename Arg, typename... Args>
  constexpr unsigned long long encode_types() {
    return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
           (encode_types<Context, Args...>() << packed_arg_bits);
  }
  
  template <typename Context, typename T>
  FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
    basic_format_arg<Context> arg;
    arg.type_ = mapped_type_constant<T, Context>::value;
    arg.value_ = arg_mapper<Context>().map(value);
    return arg;
  }
  
  template <bool IS_PACKED, typename Context, typename T,
            FMT_ENABLE_IF(IS_PACKED)>
  inline value<Context> make_arg(const T& val) {
    return arg_mapper<Context>().map(val);
  }
  
  template <bool IS_PACKED, typename Context, typename T,
            FMT_ENABLE_IF(!IS_PACKED)>
  inline basic_format_arg<Context> make_arg(const T& value) {
    return make_arg<Context>(value);
  }
  }  // namespace internal
  
  // Formatting context.
  template <typename OutputIt, typename Char> class basic_format_context {
   public:
    /** The character type for the output. */
    using char_type = Char;
  
   private:
    OutputIt out_;
    basic_format_args<basic_format_context> args_;
    internal::arg_map<basic_format_context> map_;
    internal::locale_ref loc_;
  
   public:
    using iterator = OutputIt;
    using format_arg = basic_format_arg<basic_format_context>;
    template <typename T> using formatter_type = formatter<T, char_type>;
  
    basic_format_context(const basic_format_context&) = delete;
    void operator=(const basic_format_context&) = delete;
    /**
     Constructs a ``basic_format_context`` object. References to the arguments are
     stored in the object so make sure they have appropriate lifetimes.
     */
    basic_format_context(OutputIt out,
                         basic_format_args<basic_format_context> ctx_args,
                         internal::locale_ref loc = internal::locale_ref())
        : out_(out), args_(ctx_args), loc_(loc) {}
  
    format_arg arg(int id) const { return args_.get(id); }
  
    // Checks if manual indexing is used and returns the argument with the
    // specified name.
    format_arg arg(basic_string_view<char_type> name);
  
    internal::error_handler error_handler() { return {}; }
    void on_error(const char* message) { error_handler().on_error(message); }
  
    // Returns an iterator to the beginning of the output range.
    iterator out() { return out_; }
  
    // Advances the begin iterator to ``it``.
    void advance_to(iterator it) { out_ = it; }
  
    internal::locale_ref locale() { return loc_; }
  };
  
  template <typename Char>
  using buffer_context =
      basic_format_context<std::back_insert_iterator<internal::buffer<Char>>,
                           Char>;
  using format_context = buffer_context<char>;
  using wformat_context = buffer_context<wchar_t>;
  
  /**
    \rst
    An array of references to arguments. It can be implicitly converted into
    `~fmt::basic_format_args` for passing into type-erased formatting functions
    such as `~fmt::vformat`.
    \endrst
   */
  template <typename Context, typename... Args>
  class format_arg_store
  #if FMT_GCC_VERSION < 409
      // Workaround a GCC template argument substitution bug.
      : public basic_format_args<Context>
  #endif
  {
   private:
    static const size_t num_args = sizeof...(Args);
    static const bool is_packed = num_args < internal::max_packed_args;
  
    using value_type = conditional_t<is_packed, internal::value<Context>,
                                     basic_format_arg<Context>>;
  
    // If the arguments are not packed, add one more element to mark the end.
    value_type data_[num_args + (num_args == 0 ? 1 : 0)];
  
    friend class basic_format_args<Context>;
  
   public:
    static constexpr unsigned long long types =
        is_packed ? internal::encode_types<Context, Args...>()
                  : internal::is_unpacked_bit | num_args;
  
    format_arg_store(const Args&... args)
        :
  #if FMT_GCC_VERSION < 409
          basic_format_args<Context>(*this),
  #endif
          data_{internal::make_arg<is_packed, Context>(args)...} {
    }
  };
  
  /**
    \rst
    Constructs an `~fmt::format_arg_store` object that contains references to
    arguments and can be implicitly converted to `~fmt::format_args`. `Context`
    can be omitted in which case it defaults to `~fmt::context`.
    See `~fmt::arg` for lifetime considerations.
    \endrst
   */
  template <typename Context = format_context, typename... Args>
  inline format_arg_store<Context, Args...> make_format_args(
      const Args&... args) {
    return {args...};
  }
  
  /**
    \rst
    A view of a collection of formatting arguments. To avoid lifetime issues it
    should only be used as a parameter type in type-erased functions such as
    ``vformat``::
  
      void vlog(string_view format_str, format_args args);  // OK
      format_args args = make_format_args(42);  // Error: dangling reference
    \endrst
   */
  template <typename Context> class basic_format_args {
   public:
    using size_type = int;
    using format_arg = basic_format_arg<Context>;
  
   private:
    // To reduce compiled code size per formatting function call, types of first
    // max_packed_args arguments are passed in the types_ field.
    unsigned long long types_;
    union {
      // If the number of arguments is less than max_packed_args, the argument
      // values are stored in values_, otherwise they are stored in args_.
      // This is done to reduce compiled code size as storing larger objects
      // may require more code (at least on x86-64) even if the same amount of
      // data is actually copied to stack. It saves ~10% on the bloat test.
      const internal::value<Context>* values_;
      const format_arg* args_;
    };
  
    bool is_packed() const { return (types_ & internal::is_unpacked_bit) == 0; }
  
    internal::type type(int index) const {
      int shift = index * internal::packed_arg_bits;
      unsigned int mask = (1 << internal::packed_arg_bits) - 1;
      return static_cast<internal::type>((types_ >> shift) & mask);
    }
  
    friend class internal::arg_map<Context>;
  
    void set_data(const internal::value<Context>* values) { values_ = values; }
    void set_data(const format_arg* args) { args_ = args; }
  
    format_arg do_get(int index) const {
      format_arg arg;
      if (!is_packed()) {
        auto num_args = max_size();
        if (index < num_args) arg = args_[index];
        return arg;
      }
      if (index > internal::max_packed_args) return arg;
      arg.type_ = type(index);
      if (arg.type_ == internal::type::none_type) return arg;
      internal::value<Context>& val = arg.value_;
      val = values_[index];
      return arg;
    }
  
   public:
    basic_format_args() : types_(0) {}
  
    /**
     \rst
     Constructs a `basic_format_args` object from `~fmt::format_arg_store`.
     \endrst
     */
    template <typename... Args>
    basic_format_args(const format_arg_store<Context, Args...>& store)
        : types_(store.types) {
      set_data(store.data_);
    }
  
    /**
     \rst
     Constructs a `basic_format_args` object from a dynamic set of arguments.
     \endrst
     */
    basic_format_args(const format_arg* args, int count)
        : types_(internal::is_unpacked_bit | internal::to_unsigned(count)) {
      set_data(args);
    }
  
    /** Returns the argument at specified index. */
    format_arg get(int index) const {
      format_arg arg = do_get(index);
      if (arg.type_ == internal::type::named_arg_type)
        arg = arg.value_.named_arg->template deserialize<Context>();
      return arg;
    }
  
    int max_size() const {
      unsigned long long max_packed = internal::max_packed_args;
      return static_cast<int>(is_packed() ? max_packed
                                          : types_ & ~internal::is_unpacked_bit);
    }
  };
  
  /** An alias to ``basic_format_args<context>``. */
  // It is a separate type rather than an alias to make symbols readable.
  struct format_args : basic_format_args<format_context> {
    template <typename... Args>
    format_args(Args&&... args)
        : basic_format_args<format_context>(static_cast<Args&&>(args)...) {}
  };
  struct wformat_args : basic_format_args<wformat_context> {
    template <typename... Args>
    wformat_args(Args&&... args)
        : basic_format_args<wformat_context>(static_cast<Args&&>(args)...) {}
  };
  
  template <typename Container> struct is_contiguous : std::false_type {};
  
  template <typename Char>
  struct is_contiguous<std::basic_string<Char>> : std::true_type {};
  
  template <typename Char>
  struct is_contiguous<internal::buffer<Char>> : std::true_type {};
  
  namespace internal {
  
  template <typename OutputIt>
  struct is_contiguous_back_insert_iterator : std::false_type {};
  template <typename Container>
  struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
      : is_contiguous<Container> {};
  
  template <typename Char> struct named_arg_base {
    basic_string_view<Char> name;
  
    // Serialized value<context>.
    mutable char data[sizeof(basic_format_arg<buffer_context<Char>>)];
  
    named_arg_base(basic_string_view<Char> nm) : name(nm) {}
  
    template <typename Context> basic_format_arg<Context> deserialize() const {
      basic_format_arg<Context> arg;
      std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
      return arg;
    }
  };
  
  struct view {};
  
  template <typename T, typename Char>
  struct named_arg : view, named_arg_base<Char> {
    const T& value;
  
    named_arg(basic_string_view<Char> name, const T& val)
        : named_arg_base<Char>(name), value(val) {}
  };
  
  template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
  inline void check_format_string(const S&) {
  #if defined(FMT_ENFORCE_COMPILE_STRING)
    static_assert(is_compile_string<S>::value,
                  "FMT_ENFORCE_COMPILE_STRING requires all format strings to "
                  "utilize FMT_STRING() or fmt().");
  #endif
  }
  template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
  void check_format_string(S);
  
  template <bool...> struct bool_pack;
  template <bool... Args>
  using all_true =
      std::is_same<bool_pack<Args..., true>, bool_pack<true, Args...>>;
  
  template <typename... Args, typename S, typename Char = char_t<S>>
  inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
  make_args_checked(const S& format_str,
                    const remove_reference_t<Args>&... args) {
    static_assert(
        all_true<(!std::is_base_of<view, remove_reference_t<Args>>::value ||
                  !std::is_reference<Args>::value)...>::value,
        "passing views as lvalues is disallowed");
    check_format_string<remove_const_t<remove_reference_t<Args>>...>(format_str);
    return {args...};
  }
  
  template <typename Char>
  std::basic_string<Char> vformat(
      basic_string_view<Char> format_str,
      basic_format_args<buffer_context<type_identity_t<Char>>> args);
  
  template <typename Char>
  typename buffer_context<Char>::iterator vformat_to(
      buffer<Char>& buf, basic_string_view<Char> format_str,
      basic_format_args<buffer_context<type_identity_t<Char>>> args);
  
  FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
  }  // namespace internal
  
  /**
    \rst
    Returns a named argument to be used in a formatting function. It should only
    be used in a call to a formatting function.
  
    **Example**::
  
      fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
    \endrst
   */
  template <typename S, typename T, typename Char = char_t<S>>
  inline internal::named_arg<T, Char> arg(const S& name, const T& arg) {
    static_assert(internal::is_string<S>::value, "");
    return {name, arg};
  }
  
  // Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
  template <typename S, typename T, typename Char>
  void arg(S, internal::named_arg<T, Char>) = delete;
  
  /** Formats a string and writes the output to ``out``. */
  // GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
  // vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
  template <typename OutputIt, typename S, typename Char = char_t<S>,
            FMT_ENABLE_IF(
                internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
  OutputIt vformat_to(
      OutputIt out, const S& format_str,
      basic_format_args<buffer_context<type_identity_t<Char>>> args) {
    using container = remove_reference_t<decltype(internal::get_container(out))>;
    internal::container_buffer<container> buf((internal::get_container(out)));
    internal::vformat_to(buf, to_string_view(format_str), args);
    return out;
  }
  
  template <typename Container, typename S, typename... Args,
            FMT_ENABLE_IF(
                is_contiguous<Container>::value&& internal::is_string<S>::value)>
  inline std::back_insert_iterator<Container> format_to(
      std::back_insert_iterator<Container> out, const S& format_str,
      Args&&... args) {
    return vformat_to(out, to_string_view(format_str),
                      internal::make_args_checked<Args...>(format_str, args...));
  }
  
  template <typename S, typename Char = char_t<S>>
  inline std::basic_string<Char> vformat(
      const S& format_str,
      basic_format_args<buffer_context<type_identity_t<Char>>> args) {
    return internal::vformat(to_string_view(format_str), args);
  }
  
  /**
    \rst
    Formats arguments and returns the result as a string.
  
    **Example**::
  
      #include <fmt/core.h>
      std::string message = fmt::format("The answer is {}", 42);
    \endrst
  */
  // Pass char_t as a default template parameter instead of using
  // std::basic_string<char_t<S>> to reduce the symbol size.
  template <typename S, typename... Args, typename Char = char_t<S>>
  inline std::basic_string<Char> format(const S& format_str, Args&&... args) {
    return internal::vformat(
        to_string_view(format_str),
        internal::make_args_checked<Args...>(format_str, args...));
  }
  
  FMT_API void vprint(string_view, format_args);
  FMT_API void vprint(std::FILE*, string_view, format_args);
  
  /**
    \rst
    Formats ``args`` according to specifications in ``format_str`` and writes the
    output to the file ``f``. Strings are assumed to be Unicode-encoded unless the
    ``FMT_UNICODE`` macro is set to 0.
  
    **Example**::
  
      fmt::print(stderr, "Don't {}!", "panic");
    \endrst
   */
  template <typename S, typename... Args,
            FMT_ENABLE_IF(internal::is_string<S>::value)>
  inline void print(std::FILE* f, const S& format_str, Args&&... args) {
  #if !defined(_WIN32) || FMT_UNICODE
    vprint(f, to_string_view(format_str),
           internal::make_args_checked<Args...>(format_str, args...));
  #else
    internal::vprint_mojibake(
        f, to_string_view(format_str),
        internal::make_args_checked<Args...>(format_str, args...));
  #endif
  }
  
  /**
    \rst
    Formats ``args`` according to specifications in ``format_str`` and writes
    the output to ``stdout``. Strings are assumed to be Unicode-encoded unless
    the ``FMT_UNICODE`` macro is set to 0.
  
    **Example**::
  
      fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
    \endrst
   */
  template <typename S, typename... Args,
            FMT_ENABLE_IF(internal::is_string<S>::value)>
  inline void print(const S& format_str, Args&&... args) {
  #if !defined(_WIN32) || FMT_UNICODE
    vprint(to_string_view(format_str),
           internal::make_args_checked<Args...>(format_str, args...));
  #else
    internal::vprint_mojibake(
        stdout, to_string_view(format_str),
        internal::make_args_checked<Args...>(format_str, args...));
  #endif
  }
  FMT_END_NAMESPACE
  
  #endif  // FMT_CORE_H_
  