src/vendor/fmt/ranges.h

   1 // Formatting library for C++ - experimental range support
   2 //
   3 // Copyright (c) 2012 - present, Victor Zverovich
   4 // All rights reserved.
   5 //
   6 // For the license information refer to format.h.
   7 //
   8 // Copyright (c) 2018 - present, Remotion (Igor Schulz)
   9 // All Rights Reserved
  10 // {fmt} support for ranges, containers and types tuple interface.
  11
  12 #ifndef FMT_RANGES_H_
  13 #define FMT_RANGES_H_
  14
  15 #include <initializer_list>
  16 #include <tuple>
  17 #include <type_traits>
  18
  19 #include "format.h"
  20
  21 FMT_BEGIN_NAMESPACE
  22
  23 namespace detail {
  24
  25 template <typename RangeT, typename OutputIterator>
  26 OutputIterator copy(const RangeT& range, OutputIterator out) {
  27   for (auto it = range.begin(), end = range.end(); it != end; ++it)
  28     *out++ = *it;
  29   return out;
  30 }
  31
  32 template <typename OutputIterator>
  33 OutputIterator copy(const char* str, OutputIterator out) {
  34   while (*str) *out++ = *str++;
  35   return out;
  36 }
  37
  38 template <typename OutputIterator>
  39 OutputIterator copy(char ch, OutputIterator out) {
  40   *out++ = ch;
  41   return out;
  42 }
  43
  44 template <typename OutputIterator>
  45 OutputIterator copy(wchar_t ch, OutputIterator out) {
  46   *out++ = ch;
  47   return out;
  48 }
  49
  50 // Returns true if T has a std::string-like interface, like std::string_view.
  51 template <typename T> class is_std_string_like {
  52   template <typename U>
  53   static auto check(U* p)
  54       -> decltype((void)p->find('a'), p->length(), (void)p->data(), int());
  55   template <typename> static void check(...);
  56
  57  public:
  58   static constexpr const bool value =
  59       is_string<T>::value ||
  60       std::is_convertible<T, std_string_view<char>>::value ||
  61       !std::is_void<decltype(check<T>(nullptr))>::value;
  62 };
  63
  64 template <typename Char>
  65 struct is_std_string_like<fmt::basic_string_view<Char>> : std::true_type {};
  66
  67 template <typename T> class is_map {
  68   template <typename U> static auto check(U*) -> typename U::mapped_type;
  69   template <typename> static void check(...);
  70
  71  public:
  72 #ifdef FMT_FORMAT_MAP_AS_LIST
  73   static constexpr const bool value = false;
  74 #else
  75   static constexpr const bool value =
  76       !std::is_void<decltype(check<T>(nullptr))>::value;
  77 #endif
  78 };
  79
  80 template <typename T> class is_set {
  81   template <typename U> static auto check(U*) -> typename U::key_type;
  82   template <typename> static void check(...);
  83
  84  public:
  85 #ifdef FMT_FORMAT_SET_AS_LIST
  86   static constexpr const bool value = false;
  87 #else
  88   static constexpr const bool value =
  89       !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
  90 #endif
  91 };
  92
  93 template <typename... Ts> struct conditional_helper {};
  94
  95 template <typename T, typename _ = void> struct is_range_ : std::false_type {};
  96
  97 #if !FMT_MSC_VERSION || FMT_MSC_VERSION > 1800
  98
  99 #  define FMT_DECLTYPE_RETURN(val)  \
 100     ->decltype(val) { return val; } \
 101     static_assert(                  \
 102         true, "")  // This makes it so that a semicolon is required after the
 103                    // macro, which helps clang-format handle the formatting.
 104
 105 // C array overload
 106 template <typename T, std::size_t N>
 107 auto range_begin(const T (&arr)[N]) -> const T* {
 108   return arr;
 109 }
 110 template <typename T, std::size_t N>
 111 auto range_end(const T (&arr)[N]) -> const T* {
 112   return arr + N;
 113 }
 114
 115 template <typename T, typename Enable = void>
 116 struct has_member_fn_begin_end_t : std::false_type {};
 117
 118 template <typename T>
 119 struct has_member_fn_begin_end_t<T, void_t<decltype(std::declval<T>().begin()),
 120                                            decltype(std::declval<T>().end())>>
 121     : std::true_type {};
 122
 123 // Member function overload
 124 template <typename T>
 125 auto range_begin(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).begin());
 126 template <typename T>
 127 auto range_end(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).end());
 128
 129 // ADL overload. Only participates in overload resolution if member functions
 130 // are not found.
 131 template <typename T>
 132 auto range_begin(T&& rng)
 133     -> enable_if_t<!has_member_fn_begin_end_t<T&&>::value,
 134                    decltype(begin(static_cast<T&&>(rng)))> {
 135   return begin(static_cast<T&&>(rng));
 136 }
 137 template <typename T>
 138 auto range_end(T&& rng) -> enable_if_t<!has_member_fn_begin_end_t<T&&>::value,
 139                                        decltype(end(static_cast<T&&>(rng)))> {
 140   return end(static_cast<T&&>(rng));
 141 }
 142
 143 template <typename T, typename Enable = void>
 144 struct has_const_begin_end : std::false_type {};
 145 template <typename T, typename Enable = void>
 146 struct has_mutable_begin_end : std::false_type {};
 147
 148 template <typename T>
 149 struct has_const_begin_end<
 150     T,
 151     void_t<
 152         decltype(detail::range_begin(std::declval<const remove_cvref_t<T>&>())),
 153         decltype(detail::range_end(std::declval<const remove_cvref_t<T>&>()))>>
 154     : std::true_type {};
 155
 156 template <typename T>
 157 struct has_mutable_begin_end<
 158     T, void_t<decltype(detail::range_begin(std::declval<T>())),
 159               decltype(detail::range_end(std::declval<T>())),
 160               enable_if_t<std::is_copy_constructible<T>::value>>>
 161     : std::true_type {};
 162
 163 template <typename T>
 164 struct is_range_<T, void>
 165     : std::integral_constant<bool, (has_const_begin_end<T>::value ||
 166                                     has_mutable_begin_end<T>::value)> {};
 167 #  undef FMT_DECLTYPE_RETURN
 168 #endif
 169
 170 // tuple_size and tuple_element check.
 171 template <typename T> class is_tuple_like_ {
 172   template <typename U>
 173   static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
 174   template <typename> static void check(...);
 175
 176  public:
 177   static constexpr const bool value =
 178       !std::is_void<decltype(check<T>(nullptr))>::value;
 179 };
 180
 181 // Check for integer_sequence
 182 #if defined(__cpp_lib_integer_sequence) || FMT_MSC_VERSION >= 1900
 183 template <typename T, T... N>
 184 using integer_sequence = std::integer_sequence<T, N...>;
 185 template <size_t... N> using index_sequence = std::index_sequence<N...>;
 186 template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 187 #else
 188 template <typename T, T... N> struct integer_sequence {
 189   using value_type = T;
 190
 191   static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
 192 };
 193
 194 template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
 195
 196 template <typename T, size_t N, T... Ns>
 197 struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Ns...> {};
 198 template <typename T, T... Ns>
 199 struct make_integer_sequence<T, 0, Ns...> : integer_sequence<T, Ns...> {};
 200
 201 template <size_t N>
 202 using make_index_sequence = make_integer_sequence<size_t, N>;
 203 #endif
 204
 205 template <typename T>
 206 using tuple_index_sequence = make_index_sequence<std::tuple_size<T>::value>;
 207
 208 template <typename T, typename C, bool = is_tuple_like_<T>::value>
 209 class is_tuple_formattable_ {
 210  public:
 211   static constexpr const bool value = false;
 212 };
 213 template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
 214   template <std::size_t... I>
 215   static std::true_type check2(index_sequence<I...>,
 216                                integer_sequence<bool, (I == I)...>);
 217   static std::false_type check2(...);
 218   template <std::size_t... I>
 219   static decltype(check2(
 220       index_sequence<I...>{},
 221       integer_sequence<
 222           bool, (is_formattable<typename std::tuple_element<I, T>::type,
 223                                 C>::value)...>{})) check(index_sequence<I...>);
 224
 225  public:
 226   static constexpr const bool value =
 227       decltype(check(tuple_index_sequence<T>{}))::value;
 228 };
 229
 230 template <class Tuple, class F, size_t... Is>
 231 void for_each(index_sequence<Is...>, Tuple&& tup, F&& f) noexcept {
 232   using std::get;
 233   // using free function get<I>(T) now.
 234   const int _[] = {0, ((void)f(get<Is>(tup)), 0)...};
 235   (void)_;  // blocks warnings
 236 }
 237
 238 template <class T>
 239 FMT_CONSTEXPR make_index_sequence<std::tuple_size<T>::value> get_indexes(
 240     T const&) {
 241   return {};
 242 }
 243
 244 template <class Tuple, class F> void for_each(Tuple&& tup, F&& f) {
 245   const auto indexes = get_indexes(tup);
 246   for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
 247 }
 248
 249 #if FMT_MSC_VERSION && FMT_MSC_VERSION < 1920
 250 // Older MSVC doesn't get the reference type correctly for arrays.
 251 template <typename R> struct range_reference_type_impl {
 252   using type = decltype(*detail::range_begin(std::declval<R&>()));
 253 };
 254
 255 template <typename T, std::size_t N> struct range_reference_type_impl<T[N]> {
 256   using type = T&;
 257 };
 258
 259 template <typename T>
 260 using range_reference_type = typename range_reference_type_impl<T>::type;
 261 #else
 262 template <typename Range>
 263 using range_reference_type =
 264     decltype(*detail::range_begin(std::declval<Range&>()));
 265 #endif
 266
 267 // We don't use the Range's value_type for anything, but we do need the Range's
 268 // reference type, with cv-ref stripped.
 269 template <typename Range>
 270 using uncvref_type = remove_cvref_t<range_reference_type<Range>>;
 271
 272 template <typename Range>
 273 using uncvref_first_type =
 274     remove_cvref_t<decltype(std::declval<range_reference_type<Range>>().first)>;
 275
 276 template <typename Range>
 277 using uncvref_second_type = remove_cvref_t<
 278     decltype(std::declval<range_reference_type<Range>>().second)>;
 279
 280 template <typename OutputIt> OutputIt write_delimiter(OutputIt out) {
 281   *out++ = ',';
 282   *out++ = ' ';
 283   return out;
 284 }
 285
 286 template <typename Char, typename OutputIt>
 287 auto write_range_entry(OutputIt out, basic_string_view<Char> str) -> OutputIt {
 288   return write_escaped_string(out, str);
 289 }
 290
 291 template <typename Char, typename OutputIt, typename T,
 292           FMT_ENABLE_IF(std::is_convertible<T, std_string_view<char>>::value)>
 293 inline auto write_range_entry(OutputIt out, const T& str) -> OutputIt {
 294   auto sv = std_string_view<Char>(str);
 295   return write_range_entry<Char>(out, basic_string_view<Char>(sv));
 296 }
 297
 298 template <typename Char, typename OutputIt, typename Arg,
 299           FMT_ENABLE_IF(std::is_same<Arg, Char>::value)>
 300 OutputIt write_range_entry(OutputIt out, const Arg v) {
 301   return write_escaped_char(out, v);
 302 }
 303
 304 template <
 305     typename Char, typename OutputIt, typename Arg,
 306     FMT_ENABLE_IF(!is_std_string_like<typename std::decay<Arg>::type>::value &&
 307                   !std::is_same<Arg, Char>::value)>
 308 OutputIt write_range_entry(OutputIt out, const Arg& v) {
 309   return write<Char>(out, v);
 310 }
 311
 312 }  // namespace detail
 313
 314 template <typename T> struct is_tuple_like {
 315   static constexpr const bool value =
 316       detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
 317 };
 318
 319 template <typename T, typename C> struct is_tuple_formattable {
 320   static constexpr const bool value =
 321       detail::is_tuple_formattable_<T, C>::value;
 322 };
 323
 324 template <typename TupleT, typename Char>
 325 struct formatter<TupleT, Char,
 326                  enable_if_t<fmt::is_tuple_like<TupleT>::value &&
 327                              fmt::is_tuple_formattable<TupleT, Char>::value>> {
 328  private:
 329   basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
 330   basic_string_view<Char> opening_bracket_ =
 331       detail::string_literal<Char, '('>{};
 332   basic_string_view<Char> closing_bracket_ =
 333       detail::string_literal<Char, ')'>{};
 334
 335   // C++11 generic lambda for format().
 336   template <typename FormatContext> struct format_each {
 337     template <typename T> void operator()(const T& v) {
 338       if (i > 0) out = detail::copy_str<Char>(separator, out);
 339       out = detail::write_range_entry<Char>(out, v);
 340       ++i;
 341     }
 342     int i;
 343     typename FormatContext::iterator& out;
 344     basic_string_view<Char> separator;
 345   };
 346
 347  public:
 348   FMT_CONSTEXPR formatter() {}
 349
 350   FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
 351     separator_ = sep;
 352   }
 353
 354   FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
 355                                   basic_string_view<Char> close) {
 356     opening_bracket_ = open;
 357     closing_bracket_ = close;
 358   }
 359
 360   template <typename ParseContext>
 361   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
 362     return ctx.begin();
 363   }
 364
 365   template <typename FormatContext = format_context>
 366   auto format(const TupleT& values, FormatContext& ctx) const
 367       -> decltype(ctx.out()) {
 368     auto out = ctx.out();
 369     out = detail::copy_str<Char>(opening_bracket_, out);
 370     detail::for_each(values, format_each<FormatContext>{0, out, separator_});
 371     out = detail::copy_str<Char>(closing_bracket_, out);
 372     return out;
 373   }
 374 };
 375
 376 template <typename T, typename Char> struct is_range {
 377   static constexpr const bool value =
 378       detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
 379       !std::is_convertible<T, std::basic_string<Char>>::value &&
 380       !std::is_convertible<T, detail::std_string_view<Char>>::value;
 381 };
 382
 383 namespace detail {
 384 template <typename Context> struct range_mapper {
 385   using mapper = arg_mapper<Context>;
 386
 387   template <typename T,
 388             FMT_ENABLE_IF(has_formatter<remove_cvref_t<T>, Context>::value)>
 389   static auto map(T&& value) -> T&& {
 390     return static_cast<T&&>(value);
 391   }
 392   template <typename T,
 393             FMT_ENABLE_IF(!has_formatter<remove_cvref_t<T>, Context>::value)>
 394   static auto map(T&& value)
 395       -> decltype(mapper().map(static_cast<T&&>(value))) {
 396     return mapper().map(static_cast<T&&>(value));
 397   }
 398 };
 399
 400 template <typename Char, typename Element>
 401 using range_formatter_type = conditional_t<
 402     is_formattable<Element, Char>::value,
 403     formatter<remove_cvref_t<decltype(range_mapper<buffer_context<Char>>{}.map(
 404                   std::declval<Element>()))>,
 405               Char>,
 406     fallback_formatter<Element, Char>>;
 407
 408 template <typename R>
 409 using maybe_const_range =
 410     conditional_t<has_const_begin_end<R>::value, const R, R>;
 411
 412 // Workaround a bug in MSVC 2015 and earlier.
 413 #if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
 414 template <typename R, typename Char>
 415 struct is_formattable_delayed
 416     : disjunction<
 417           is_formattable<uncvref_type<maybe_const_range<R>>, Char>,
 418           has_fallback_formatter<uncvref_type<maybe_const_range<R>>, Char>> {};
 419 #endif
 420
 421 }  // namespace detail
 422
 423 template <typename T, typename Char, typename Enable = void>
 424 struct range_formatter;
 425
 426 template <typename T, typename Char>
 427 struct range_formatter<
 428     T, Char,
 429     enable_if_t<conjunction<
 430         std::is_same<T, remove_cvref_t<T>>,
 431         disjunction<is_formattable<T, Char>,
 432                     detail::has_fallback_formatter<T, Char>>>::value>> {
 433  private:
 434   detail::range_formatter_type<Char, T> underlying_;
 435   bool custom_specs_ = false;
 436   basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
 437   basic_string_view<Char> opening_bracket_ =
 438       detail::string_literal<Char, '['>{};
 439   basic_string_view<Char> closing_bracket_ =
 440       detail::string_literal<Char, ']'>{};
 441
 442   template <class U>
 443   FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, int)
 444       -> decltype(u.set_debug_format()) {
 445     u.set_debug_format();
 446   }
 447
 448   template <class U>
 449   FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
 450
 451   FMT_CONSTEXPR void maybe_set_debug_format() {
 452     maybe_set_debug_format(underlying_, 0);
 453   }
 454
 455  public:
 456   FMT_CONSTEXPR range_formatter() {}
 457
 458   FMT_CONSTEXPR auto underlying() -> detail::range_formatter_type<Char, T>& {
 459     return underlying_;
 460   }
 461
 462   FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
 463     separator_ = sep;
 464   }
 465
 466   FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
 467                                   basic_string_view<Char> close) {
 468     opening_bracket_ = open;
 469     closing_bracket_ = close;
 470   }
 471
 472   template <typename ParseContext>
 473   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
 474     auto it = ctx.begin();
 475     auto end = ctx.end();
 476     if (it == end || *it == '}') {
 477       maybe_set_debug_format();
 478       return it;
 479     }
 480
 481     if (*it == 'n') {
 482       set_brackets({}, {});
 483       ++it;
 484     }
 485
 486     if (*it == '}') {
 487       maybe_set_debug_format();
 488       return it;
 489     }
 490
 491     if (*it != ':')
 492       FMT_THROW(format_error("no other top-level range formatters supported"));
 493
 494     custom_specs_ = true;
 495     ++it;
 496     ctx.advance_to(it);
 497     return underlying_.parse(ctx);
 498   }
 499
 500   template <typename R, class FormatContext>
 501   auto format(R&& range, FormatContext& ctx) const -> decltype(ctx.out()) {
 502     detail::range_mapper<buffer_context<Char>> mapper;
 503     auto out = ctx.out();
 504     out = detail::copy_str<Char>(opening_bracket_, out);
 505     int i = 0;
 506     auto it = detail::range_begin(range);
 507     auto end = detail::range_end(range);
 508     for (; it != end; ++it) {
 509       if (i > 0) out = detail::copy_str<Char>(separator_, out);
 510       ;
 511       ctx.advance_to(out);
 512       out = underlying_.format(mapper.map(*it), ctx);
 513       ++i;
 514     }
 515     out = detail::copy_str<Char>(closing_bracket_, out);
 516     return out;
 517   }
 518 };
 519
 520 enum class range_format { disabled, map, set, sequence, string, debug_string };
 521
 522 namespace detail {
 523 template <typename T> struct range_format_kind_ {
 524   static constexpr auto value = std::is_same<range_reference_type<T>, T>::value
 525                                     ? range_format::disabled
 526                                 : is_map<T>::value ? range_format::map
 527                                 : is_set<T>::value ? range_format::set
 528                                                    : range_format::sequence;
 529 };
 530
 531 template <range_format K, typename R, typename Char, typename Enable = void>
 532 struct range_default_formatter;
 533
 534 template <range_format K>
 535 using range_format_constant = std::integral_constant<range_format, K>;
 536
 537 template <range_format K, typename R, typename Char>
 538 struct range_default_formatter<
 539     K, R, Char,
 540     enable_if_t<(K == range_format::sequence || K == range_format::map ||
 541                  K == range_format::set)>> {
 542   using range_type = detail::maybe_const_range<R>;
 543   range_formatter<detail::uncvref_type<range_type>, Char> underlying_;
 544
 545   FMT_CONSTEXPR range_default_formatter() { init(range_format_constant<K>()); }
 546
 547   FMT_CONSTEXPR void init(range_format_constant<range_format::set>) {
 548     underlying_.set_brackets(detail::string_literal<Char, '{'>{},
 549                              detail::string_literal<Char, '}'>{});
 550   }
 551
 552   FMT_CONSTEXPR void init(range_format_constant<range_format::map>) {
 553     underlying_.set_brackets(detail::string_literal<Char, '{'>{},
 554                              detail::string_literal<Char, '}'>{});
 555     underlying_.underlying().set_brackets({}, {});
 556     underlying_.underlying().set_separator(
 557         detail::string_literal<Char, ':', ' '>{});
 558   }
 559
 560   FMT_CONSTEXPR void init(range_format_constant<range_format::sequence>) {}
 561
 562   template <typename ParseContext>
 563   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
 564     return underlying_.parse(ctx);
 565   }
 566
 567   template <typename FormatContext>
 568   auto format(range_type& range, FormatContext& ctx) const
 569       -> decltype(ctx.out()) {
 570     return underlying_.format(range, ctx);
 571   }
 572 };
 573 }  // namespace detail
 574
 575 template <typename T, typename Char, typename Enable = void>
 576 struct range_format_kind
 577     : conditional_t<
 578           is_range<T, Char>::value, detail::range_format_kind_<T>,
 579           std::integral_constant<range_format, range_format::disabled>> {};
 580
 581 template <typename R, typename Char>
 582 struct formatter<
 583     R, Char,
 584     enable_if_t<conjunction<bool_constant<range_format_kind<R, Char>::value !=
 585                                           range_format::disabled>
 586 // Workaround a bug in MSVC 2015 and earlier.
 587 #if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
 588                             ,
 589                             detail::is_formattable_delayed<R, Char>
 590 #endif
 591                             >::value>>
 592     : detail::range_default_formatter<range_format_kind<R, Char>::value, R,
 593                                       Char> {
 594 };
 595
 596 template <typename Char, typename... T> struct tuple_join_view : detail::view {
 597   const std::tuple<T...>& tuple;
 598   basic_string_view<Char> sep;
 599
 600   tuple_join_view(const std::tuple<T...>& t, basic_string_view<Char> s)
 601       : tuple(t), sep{s} {}
 602 };
 603
 604 template <typename Char, typename... T>
 605 using tuple_arg_join = tuple_join_view<Char, T...>;
 606
 607 // Define FMT_TUPLE_JOIN_SPECIFIERS to enable experimental format specifiers
 608 // support in tuple_join. It is disabled by default because of issues with
 609 // the dynamic width and precision.
 610 #ifndef FMT_TUPLE_JOIN_SPECIFIERS
 611 #  define FMT_TUPLE_JOIN_SPECIFIERS 0
 612 #endif
 613
 614 template <typename Char, typename... T>
 615 struct formatter<tuple_join_view<Char, T...>, Char> {
 616   template <typename ParseContext>
 617   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
 618     return do_parse(ctx, std::integral_constant<size_t, sizeof...(T)>());
 619   }
 620
 621   template <typename FormatContext>
 622   auto format(const tuple_join_view<Char, T...>& value,
 623               FormatContext& ctx) const -> typename FormatContext::iterator {
 624     return do_format(value, ctx,
 625                      std::integral_constant<size_t, sizeof...(T)>());
 626   }
 627
 628  private:
 629   std::tuple<formatter<typename std::decay<T>::type, Char>...> formatters_;
 630
 631   template <typename ParseContext>
 632   FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
 633                               std::integral_constant<size_t, 0>)
 634       -> decltype(ctx.begin()) {
 635     return ctx.begin();
 636   }
 637
 638   template <typename ParseContext, size_t N>
 639   FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
 640                               std::integral_constant<size_t, N>)
 641       -> decltype(ctx.begin()) {
 642     auto end = ctx.begin();
 643 #if FMT_TUPLE_JOIN_SPECIFIERS
 644     end = std::get<sizeof...(T) - N>(formatters_).parse(ctx);
 645     if (N > 1) {
 646       auto end1 = do_parse(ctx, std::integral_constant<size_t, N - 1>());
 647       if (end != end1)
 648         FMT_THROW(format_error("incompatible format specs for tuple elements"));
 649     }
 650 #endif
 651     return end;
 652   }
 653
 654   template <typename FormatContext>
 655   auto do_format(const tuple_join_view<Char, T...>&, FormatContext& ctx,
 656                  std::integral_constant<size_t, 0>) const ->
 657       typename FormatContext::iterator {
 658     return ctx.out();
 659   }
 660
 661   template <typename FormatContext, size_t N>
 662   auto do_format(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
 663                  std::integral_constant<size_t, N>) const ->
 664       typename FormatContext::iterator {
 665     auto out = std::get<sizeof...(T) - N>(formatters_)
 666                    .format(std::get<sizeof...(T) - N>(value.tuple), ctx);
 667     if (N > 1) {
 668       out = std::copy(value.sep.begin(), value.sep.end(), out);
 669       ctx.advance_to(out);
 670       return do_format(value, ctx, std::integral_constant<size_t, N - 1>());
 671     }
 672     return out;
 673   }
 674 };
 675
 676 FMT_MODULE_EXPORT_BEGIN
 677
 678 /**
 679   \rst
 680   Returns an object that formats `tuple` with elements separated by `sep`.
 681
 682   **Example**::
 683
 684     std::tuple<int, char> t = {1, 'a'};
 685     fmt::print("{}", fmt::join(t, ", "));
 686     // Output: "1, a"
 687   \endrst
 688  */
 689 template <typename... T>
 690 FMT_CONSTEXPR auto join(const std::tuple<T...>& tuple, string_view sep)
 691     -> tuple_join_view<char, T...> {
 692   return {tuple, sep};
 693 }
 694
 695 template <typename... T>
 696 FMT_CONSTEXPR auto join(const std::tuple<T...>& tuple,
 697                         basic_string_view<wchar_t> sep)
 698     -> tuple_join_view<wchar_t, T...> {
 699   return {tuple, sep};
 700 }
 701
 702 /**
 703   \rst
 704   Returns an object that formats `initializer_list` with elements separated by
 705   `sep`.
 706
 707   **Example**::
 708
 709     fmt::print("{}", fmt::join({1, 2, 3}, ", "));
 710     // Output: "1, 2, 3"
 711   \endrst
 712  */
 713 template <typename T>
 714 auto join(std::initializer_list<T> list, string_view sep)
 715     -> join_view<const T*, const T*> {
 716   return join(std::begin(list), std::end(list), sep);
 717 }
 718
 719 FMT_MODULE_EXPORT_END
 720 FMT_END_NAMESPACE
 721
 722 #endif  // FMT_RANGES_H_