1 // Pair implementation -*- C++ -*- 2 3 // Copyright (C) 2001-2022 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /* 26 * 27 * Copyright (c) 1994 28 * Hewlett-Packard Company 29 * 30 * Permission to use, copy, modify, distribute and sell this software 31 * and its documentation for any purpose is hereby granted without fee, 32 * provided that the above copyright notice appear in all copies and 33 * that both that copyright notice and this permission notice appear 34 * in supporting documentation. Hewlett-Packard Company makes no 35 * representations about the suitability of this software for any 36 * purpose. It is provided "as is" without express or implied warranty. 37 * 38 * 39 * Copyright (c) 1996,1997 40 * Silicon Graphics Computer Systems, Inc. 41 * 42 * Permission to use, copy, modify, distribute and sell this software 43 * and its documentation for any purpose is hereby granted without fee, 44 * provided that the above copyright notice appear in all copies and 45 * that both that copyright notice and this permission notice appear 46 * in supporting documentation. Silicon Graphics makes no 47 * representations about the suitability of this software for any 48 * purpose. It is provided "as is" without express or implied warranty. 49 */ 50 51 /** @file bits/stl_pair.h 52 * This is an internal header file, included by other library headers. 53 * Do not attempt to use it directly. @headername{utility} 54 */ 55 56 #ifndef _STL_PAIR_H 57 #define _STL_PAIR_H 1 58 59 #if __cplusplus >= 201103L 60 # include <type_traits> // for std::__decay_and_strip 61 # include <bits/move.h> // for std::move / std::forward, and std::swap 62 # include <bits/utility.h> // for std::tuple_element, std::tuple_size 63 #endif 64 #if __cplusplus >= 202002L 65 # include <compare> 66 # define __cpp_lib_constexpr_utility 201811L 67 #endif 68 69 namespace std _GLIBCXX_VISIBILITY(default) 70 { 71 _GLIBCXX_BEGIN_NAMESPACE_VERSION 72 73 /** 74 * @addtogroup utilities 75 * @{ 76 */ 77 78 #if __cplusplus >= 201103L 79 /// Tag type for piecewise construction of std::pair objects. 80 struct piecewise_construct_t { explicit piecewise_construct_t() = default; }; 81 82 /// Tag for piecewise construction of std::pair objects. 83 _GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct = 84 piecewise_construct_t(); 85 86 /// @cond undocumented 87 88 // Forward declarations. 89 template<typename...> 90 class tuple; 91 92 template<size_t...> 93 struct _Index_tuple; 94 95 #if ! __cpp_lib_concepts 96 // Concept utility functions, reused in conditionally-explicit 97 // constructors. 98 // See PR 70437, don't look at is_constructible or 99 // is_convertible if the types are the same to 100 // avoid querying those properties for incomplete types. 101 template <bool, typename _T1, typename _T2> 102 struct _PCC 103 { 104 template <typename _U1, typename _U2> 105 static constexpr bool _ConstructiblePair() 106 { 107 return __and_<is_constructible<_T1, const _U1&>, 108 is_constructible<_T2, const _U2&>>::value; 109 } 110 111 template <typename _U1, typename _U2> 112 static constexpr bool _ImplicitlyConvertiblePair() 113 { 114 return __and_<is_convertible<const _U1&, _T1>, 115 is_convertible<const _U2&, _T2>>::value; 116 } 117 118 template <typename _U1, typename _U2> 119 static constexpr bool _MoveConstructiblePair() 120 { 121 return __and_<is_constructible<_T1, _U1&&>, 122 is_constructible<_T2, _U2&&>>::value; 123 } 124 125 template <typename _U1, typename _U2> 126 static constexpr bool _ImplicitlyMoveConvertiblePair() 127 { 128 return __and_<is_convertible<_U1&&, _T1>, 129 is_convertible<_U2&&, _T2>>::value; 130 } 131 }; 132 133 template <typename _T1, typename _T2> 134 struct _PCC<false, _T1, _T2> 135 { 136 template <typename _U1, typename _U2> 137 static constexpr bool _ConstructiblePair() 138 { 139 return false; 140 } 141 142 template <typename _U1, typename _U2> 143 static constexpr bool _ImplicitlyConvertiblePair() 144 { 145 return false; 146 } 147 148 template <typename _U1, typename _U2> 149 static constexpr bool _MoveConstructiblePair() 150 { 151 return false; 152 } 153 154 template <typename _U1, typename _U2> 155 static constexpr bool _ImplicitlyMoveConvertiblePair() 156 { 157 return false; 158 } 159 }; 160 #endif // lib concepts 161 #endif // C++11 162 163 template<typename _U1, typename _U2> class __pair_base 164 { 165 #if __cplusplus >= 201103L && ! __cpp_lib_concepts 166 template<typename _T1, typename _T2> friend struct pair; 167 __pair_base() = default; 168 ~__pair_base() = default; 169 __pair_base(const __pair_base&) = default; 170 __pair_base& operator=(const __pair_base&) = delete; 171 #endif // C++11 172 }; 173 174 /// @endcond 175 176 /** 177 * @brief Struct holding two objects of arbitrary type. 178 * 179 * @tparam _T1 Type of first object. 180 * @tparam _T2 Type of second object. 181 * 182 * <https://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html> 183 */ 184 template<typename _T1, typename _T2> 185 struct pair 186 : public __pair_base<_T1, _T2> 187 { 188 typedef _T1 first_type; ///< The type of the `first` member 189 typedef _T2 second_type; ///< The type of the `second` member 190 191 _T1 first; ///< The first member 192 _T2 second; ///< The second member 193 194 #if __cplusplus >= 201103L 195 constexpr pair(const pair&) = default; ///< Copy constructor 196 constexpr pair(pair&&) = default; ///< Move constructor 197 198 template<typename... _Args1, typename... _Args2> 199 _GLIBCXX20_CONSTEXPR 200 pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>); 201 202 /// Swap the first members and then the second members. 203 _GLIBCXX20_CONSTEXPR void 204 swap(pair& __p) 205 noexcept(__and_<__is_nothrow_swappable<_T1>, 206 __is_nothrow_swappable<_T2>>::value) 207 { 208 using std::swap; 209 swap(first, __p.first); 210 swap(second, __p.second); 211 } 212 213 private: 214 template<typename... _Args1, size_t... _Indexes1, 215 typename... _Args2, size_t... _Indexes2> 216 _GLIBCXX20_CONSTEXPR 217 pair(tuple<_Args1...>&, tuple<_Args2...>&, 218 _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>); 219 public: 220 221 #if __cpp_lib_concepts 222 // C++20 implementation using concepts, explicit(bool), fully constexpr. 223 224 /// Default constructor 225 constexpr 226 explicit(__not_<__and_<__is_implicitly_default_constructible<_T1>, 227 __is_implicitly_default_constructible<_T2>>>()) 228 pair() 229 requires is_default_constructible_v<_T1> 230 && is_default_constructible_v<_T2> 231 : first(), second() 232 { } 233 234 private: 235 236 /// @cond undocumented 237 template<typename _U1, typename _U2> 238 static constexpr bool 239 _S_constructible() 240 { 241 if constexpr (is_constructible_v<_T1, _U1>) 242 return is_constructible_v<_T2, _U2>; 243 return false; 244 } 245 246 template<typename _U1, typename _U2> 247 static constexpr bool 248 _S_nothrow_constructible() 249 { 250 if constexpr (is_nothrow_constructible_v<_T1, _U1>) 251 return is_nothrow_constructible_v<_T2, _U2>; 252 return false; 253 } 254 255 template<typename _U1, typename _U2> 256 static constexpr bool 257 _S_convertible() 258 { 259 if constexpr (is_convertible_v<_U1, _T1>) 260 return is_convertible_v<_U2, _T2>; 261 return false; 262 } 263 /// @endcond 264 265 public: 266 267 /// Constructor accepting lvalues of `first_type` and `second_type` 268 constexpr explicit(!_S_convertible<const _T1&, const _T2&>()) 269 pair(const _T1& __x, const _T2& __y) 270 noexcept(_S_nothrow_constructible<const _T1&, const _T2&>()) 271 requires (_S_constructible<const _T1&, const _T2&>()) 272 : first(__x), second(__y) 273 { } 274 275 /// Constructor accepting two values of arbitrary types 276 template<typename _U1, typename _U2> 277 requires (_S_constructible<_U1, _U2>()) 278 constexpr explicit(!_S_convertible<_U1, _U2>()) 279 pair(_U1&& __x, _U2&& __y) 280 noexcept(_S_nothrow_constructible<_U1, _U2>()) 281 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) 282 { } 283 284 /// Converting constructor from a `pair<U1, U2>` lvalue 285 template<typename _U1, typename _U2> 286 requires (_S_constructible<const _U1&, const _U2&>()) 287 constexpr explicit(!_S_convertible<const _U1&, const _U2&>()) 288 pair(const pair<_U1, _U2>& __p) 289 noexcept(_S_nothrow_constructible<const _U1&, const _U2&>()) 290 : first(__p.first), second(__p.second) 291 { } 292 293 /// Converting constructor from a `pair<U1, U2>` rvalue 294 template<typename _U1, typename _U2> 295 requires (_S_constructible<_U1, _U2>()) 296 constexpr explicit(!_S_convertible<_U1, _U2>()) 297 pair(pair<_U1, _U2>&& __p) 298 noexcept(_S_nothrow_constructible<_U1, _U2>()) 299 : first(std::forward<_U1>(__p.first)), 300 second(std::forward<_U2>(__p.second)) 301 { } 302 303 private: 304 /// @cond undocumented 305 template<typename _U1, typename _U2> 306 static constexpr bool 307 _S_assignable() 308 { 309 if constexpr (is_assignable_v<_T1&, _U1>) 310 return is_assignable_v<_T2&, _U2>; 311 return false; 312 } 313 314 template<typename _U1, typename _U2> 315 static constexpr bool 316 _S_nothrow_assignable() 317 { 318 if constexpr (is_nothrow_assignable_v<_T1&, _U1>) 319 return is_nothrow_assignable_v<_T2&, _U2>; 320 return false; 321 } 322 /// @endcond 323 324 public: 325 326 pair& operator=(const pair&) = delete; 327 328 /// Copy assignment operator 329 constexpr pair& 330 operator=(const pair& __p) 331 noexcept(_S_nothrow_assignable<const _T1&, const _T2&>()) 332 requires (_S_assignable<const _T1&, const _T2&>()) 333 { 334 first = __p.first; 335 second = __p.second; 336 return *this; 337 } 338 339 /// Move assignment operator 340 constexpr pair& 341 operator=(pair&& __p) 342 noexcept(_S_nothrow_assignable<_T1, _T2>()) 343 requires (_S_assignable<_T1, _T2>()) 344 { 345 first = std::forward<first_type>(__p.first); 346 second = std::forward<second_type>(__p.second); 347 return *this; 348 } 349 350 /// Converting assignment from a `pair<U1, U2>` lvalue 351 template<typename _U1, typename _U2> 352 constexpr pair& 353 operator=(const pair<_U1, _U2>& __p) 354 noexcept(_S_nothrow_assignable<const _U1&, const _U2&>()) 355 requires (_S_assignable<const _U1&, const _U2&>()) 356 { 357 first = __p.first; 358 second = __p.second; 359 return *this; 360 } 361 362 /// Converting assignment from a `pair<U1, U2>` rvalue 363 template<typename _U1, typename _U2> 364 constexpr pair& 365 operator=(pair<_U1, _U2>&& __p) 366 noexcept(_S_nothrow_assignable<_U1, _U2>()) 367 requires (_S_assignable<_U1, _U2>()) 368 { 369 first = std::forward<_U1>(__p.first); 370 second = std::forward<_U2>(__p.second); 371 return *this; 372 } 373 #else 374 // C++11/14/17 implementation using enable_if, partially constexpr. 375 376 /** The default constructor creates @c first and @c second using their 377 * respective default constructors. */ 378 template <typename _U1 = _T1, 379 typename _U2 = _T2, 380 typename enable_if<__and_< 381 __is_implicitly_default_constructible<_U1>, 382 __is_implicitly_default_constructible<_U2>> 383 ::value, bool>::type = true> 384 constexpr pair() 385 : first(), second() { } 386 387 template <typename _U1 = _T1, 388 typename _U2 = _T2, 389 typename enable_if<__and_< 390 is_default_constructible<_U1>, 391 is_default_constructible<_U2>, 392 __not_< 393 __and_<__is_implicitly_default_constructible<_U1>, 394 __is_implicitly_default_constructible<_U2>>>> 395 ::value, bool>::type = false> 396 explicit constexpr pair() 397 : first(), second() { } 398 399 // Shortcut for constraining the templates that don't take pairs. 400 /// @cond undocumented 401 using _PCCP = _PCC<true, _T1, _T2>; 402 /// @endcond 403 404 /// Construct from two const lvalues, allowing implicit conversions. 405 template<typename _U1 = _T1, typename _U2=_T2, typename 406 enable_if<_PCCP::template 407 _ConstructiblePair<_U1, _U2>() 408 && _PCCP::template 409 _ImplicitlyConvertiblePair<_U1, _U2>(), 410 bool>::type=true> 411 constexpr pair(const _T1& __a, const _T2& __b) 412 : first(__a), second(__b) { } 413 414 /// Construct from two const lvalues, disallowing implicit conversions. 415 template<typename _U1 = _T1, typename _U2=_T2, typename 416 enable_if<_PCCP::template 417 _ConstructiblePair<_U1, _U2>() 418 && !_PCCP::template 419 _ImplicitlyConvertiblePair<_U1, _U2>(), 420 bool>::type=false> 421 explicit constexpr pair(const _T1& __a, const _T2& __b) 422 : first(__a), second(__b) { } 423 424 // Shortcut for constraining the templates that take pairs. 425 /// @cond undocumented 426 template <typename _U1, typename _U2> 427 using _PCCFP = _PCC<!is_same<_T1, _U1>::value 428 || !is_same<_T2, _U2>::value, 429 _T1, _T2>; 430 /// @endcond 431 432 template<typename _U1, typename _U2, typename 433 enable_if<_PCCFP<_U1, _U2>::template 434 _ConstructiblePair<_U1, _U2>() 435 && _PCCFP<_U1, _U2>::template 436 _ImplicitlyConvertiblePair<_U1, _U2>(), 437 bool>::type=true> 438 constexpr pair(const pair<_U1, _U2>& __p) 439 : first(__p.first), second(__p.second) { } 440 441 template<typename _U1, typename _U2, typename 442 enable_if<_PCCFP<_U1, _U2>::template 443 _ConstructiblePair<_U1, _U2>() 444 && !_PCCFP<_U1, _U2>::template 445 _ImplicitlyConvertiblePair<_U1, _U2>(), 446 bool>::type=false> 447 explicit constexpr pair(const pair<_U1, _U2>& __p) 448 : first(__p.first), second(__p.second) { } 449 450 #if _GLIBCXX_USE_DEPRECATED 451 #if defined(__DEPRECATED) 452 # define _GLIBCXX_DEPRECATED_PAIR_CTOR \ 453 __attribute__ ((__deprecated__ ("use 'nullptr' instead of '0' to " \ 454 "initialize std::pair of move-only " \ 455 "type and pointer"))) 456 #else 457 # define _GLIBCXX_DEPRECATED_PAIR_CTOR 458 #endif 459 460 private: 461 /// @cond undocumented 462 463 // A type which can be constructed from literal zero, but not nullptr 464 struct __zero_as_null_pointer_constant 465 { 466 __zero_as_null_pointer_constant(int __zero_as_null_pointer_constant::*) 467 { } 468 template<typename _Tp, 469 typename = __enable_if_t<is_null_pointer<_Tp>::value>> 470 __zero_as_null_pointer_constant(_Tp) = delete; 471 }; 472 /// @endcond 473 public: 474 475 // Deprecated extensions to DR 811. 476 // These allow construction from an rvalue and a literal zero, 477 // in cases where the standard says the zero should be deduced as int 478 template<typename _U1, 479 __enable_if_t<__and_<__not_<is_reference<_U1>>, 480 is_pointer<_T2>, 481 is_constructible<_T1, _U1>, 482 __not_<is_constructible<_T1, const _U1&>>, 483 is_convertible<_U1, _T1>>::value, 484 bool> = true> 485 _GLIBCXX_DEPRECATED_PAIR_CTOR 486 constexpr 487 pair(_U1&& __x, __zero_as_null_pointer_constant, ...) 488 : first(std::forward<_U1>(__x)), second(nullptr) { } 489 490 template<typename _U1, 491 __enable_if_t<__and_<__not_<is_reference<_U1>>, 492 is_pointer<_T2>, 493 is_constructible<_T1, _U1>, 494 __not_<is_constructible<_T1, const _U1&>>, 495 __not_<is_convertible<_U1, _T1>>>::value, 496 bool> = false> 497 _GLIBCXX_DEPRECATED_PAIR_CTOR 498 explicit constexpr 499 pair(_U1&& __x, __zero_as_null_pointer_constant, ...) 500 : first(std::forward<_U1>(__x)), second(nullptr) { } 501 502 template<typename _U2, 503 __enable_if_t<__and_<is_pointer<_T1>, 504 __not_<is_reference<_U2>>, 505 is_constructible<_T2, _U2>, 506 __not_<is_constructible<_T2, const _U2&>>, 507 is_convertible<_U2, _T2>>::value, 508 bool> = true> 509 _GLIBCXX_DEPRECATED_PAIR_CTOR 510 constexpr 511 pair(__zero_as_null_pointer_constant, _U2&& __y, ...) 512 : first(nullptr), second(std::forward<_U2>(__y)) { } 513 514 template<typename _U2, 515 __enable_if_t<__and_<is_pointer<_T1>, 516 __not_<is_reference<_U2>>, 517 is_constructible<_T2, _U2>, 518 __not_<is_constructible<_T2, const _U2&>>, 519 __not_<is_convertible<_U2, _T2>>>::value, 520 bool> = false> 521 _GLIBCXX_DEPRECATED_PAIR_CTOR 522 explicit constexpr 523 pair(__zero_as_null_pointer_constant, _U2&& __y, ...) 524 : first(nullptr), second(std::forward<_U2>(__y)) { } 525 #undef _GLIBCXX_DEPRECATED_PAIR_CTOR 526 #endif 527 528 template<typename _U1, typename _U2, typename 529 enable_if<_PCCP::template 530 _MoveConstructiblePair<_U1, _U2>() 531 && _PCCP::template 532 _ImplicitlyMoveConvertiblePair<_U1, _U2>(), 533 bool>::type=true> 534 constexpr pair(_U1&& __x, _U2&& __y) 535 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { } 536 537 template<typename _U1, typename _U2, typename 538 enable_if<_PCCP::template 539 _MoveConstructiblePair<_U1, _U2>() 540 && !_PCCP::template 541 _ImplicitlyMoveConvertiblePair<_U1, _U2>(), 542 bool>::type=false> 543 explicit constexpr pair(_U1&& __x, _U2&& __y) 544 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { } 545 546 547 template<typename _U1, typename _U2, typename 548 enable_if<_PCCFP<_U1, _U2>::template 549 _MoveConstructiblePair<_U1, _U2>() 550 && _PCCFP<_U1, _U2>::template 551 _ImplicitlyMoveConvertiblePair<_U1, _U2>(), 552 bool>::type=true> 553 constexpr pair(pair<_U1, _U2>&& __p) 554 : first(std::forward<_U1>(__p.first)), 555 second(std::forward<_U2>(__p.second)) { } 556 557 template<typename _U1, typename _U2, typename 558 enable_if<_PCCFP<_U1, _U2>::template 559 _MoveConstructiblePair<_U1, _U2>() 560 && !_PCCFP<_U1, _U2>::template 561 _ImplicitlyMoveConvertiblePair<_U1, _U2>(), 562 bool>::type=false> 563 explicit constexpr pair(pair<_U1, _U2>&& __p) 564 : first(std::forward<_U1>(__p.first)), 565 second(std::forward<_U2>(__p.second)) { } 566 567 pair& 568 operator=(__conditional_t<__and_<is_copy_assignable<_T1>, 569 is_copy_assignable<_T2>>::value, 570 const pair&, const __nonesuch&> __p) 571 { 572 first = __p.first; 573 second = __p.second; 574 return *this; 575 } 576 577 pair& 578 operator=(__conditional_t<__and_<is_move_assignable<_T1>, 579 is_move_assignable<_T2>>::value, 580 pair&&, __nonesuch&&> __p) 581 noexcept(__and_<is_nothrow_move_assignable<_T1>, 582 is_nothrow_move_assignable<_T2>>::value) 583 { 584 first = std::forward<first_type>(__p.first); 585 second = std::forward<second_type>(__p.second); 586 return *this; 587 } 588 589 template<typename _U1, typename _U2> 590 typename enable_if<__and_<is_assignable<_T1&, const _U1&>, 591 is_assignable<_T2&, const _U2&>>::value, 592 pair&>::type 593 operator=(const pair<_U1, _U2>& __p) 594 { 595 first = __p.first; 596 second = __p.second; 597 return *this; 598 } 599 600 template<typename _U1, typename _U2> 601 typename enable_if<__and_<is_assignable<_T1&, _U1&&>, 602 is_assignable<_T2&, _U2&&>>::value, 603 pair&>::type 604 operator=(pair<_U1, _U2>&& __p) 605 { 606 first = std::forward<_U1>(__p.first); 607 second = std::forward<_U2>(__p.second); 608 return *this; 609 } 610 #endif // lib concepts 611 #else 612 // C++03 implementation 613 614 // _GLIBCXX_RESOLVE_LIB_DEFECTS 615 // 265. std::pair::pair() effects overly restrictive 616 /** The default constructor creates @c first and @c second using their 617 * respective default constructors. */ 618 pair() : first(), second() { } 619 620 /// Two objects may be passed to a `pair` constructor to be copied. 621 pair(const _T1& __a, const _T2& __b) 622 : first(__a), second(__b) { } 623 624 /// Templated constructor to convert from other pairs. 625 template<typename _U1, typename _U2> 626 pair(const pair<_U1, _U2>& __p) 627 : first(__p.first), second(__p.second) { } 628 #endif // C++11 629 }; 630 631 /// @relates pair @{ 632 633 #if __cpp_deduction_guides >= 201606 634 template<typename _T1, typename _T2> pair(_T1, _T2) -> pair<_T1, _T2>; 635 #endif 636 637 /// Two pairs of the same type are equal iff their members are equal. 638 template<typename _T1, typename _T2> 639 inline _GLIBCXX_CONSTEXPR bool 640 operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 641 { return __x.first == __y.first && __x.second == __y.second; } 642 643 #if __cpp_lib_three_way_comparison && __cpp_lib_concepts 644 template<typename _T1, typename _T2> 645 constexpr common_comparison_category_t<__detail::__synth3way_t<_T1>, 646 __detail::__synth3way_t<_T2>> 647 operator<=>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 648 { 649 if (auto __c = __detail::__synth3way(__x.first, __y.first); __c != 0) 650 return __c; 651 return __detail::__synth3way(__x.second, __y.second); 652 } 653 #else 654 /** Defines a lexicographical order for pairs. 655 * 656 * For two pairs of the same type, `P` is ordered before `Q` if 657 * `P.first` is less than `Q.first`, or if `P.first` and `Q.first` 658 * are equivalent (neither is less than the other) and `P.second` is less 659 * than `Q.second`. 660 */ 661 template<typename _T1, typename _T2> 662 inline _GLIBCXX_CONSTEXPR bool 663 operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 664 { return __x.first < __y.first 665 || (!(__y.first < __x.first) && __x.second < __y.second); } 666 667 /// Uses @c operator== to find the result. 668 template<typename _T1, typename _T2> 669 inline _GLIBCXX_CONSTEXPR bool 670 operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 671 { return !(__x == __y); } 672 673 /// Uses @c operator< to find the result. 674 template<typename _T1, typename _T2> 675 inline _GLIBCXX_CONSTEXPR bool 676 operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 677 { return __y < __x; } 678 679 /// Uses @c operator< to find the result. 680 template<typename _T1, typename _T2> 681 inline _GLIBCXX_CONSTEXPR bool 682 operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 683 { return !(__y < __x); } 684 685 /// Uses @c operator< to find the result. 686 template<typename _T1, typename _T2> 687 inline _GLIBCXX_CONSTEXPR bool 688 operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) 689 { return !(__x < __y); } 690 #endif // !(three_way_comparison && concepts) 691 692 #if __cplusplus >= 201103L 693 /** Swap overload for pairs. Calls std::pair::swap(). 694 * 695 * @note This std::swap overload is not declared in C++03 mode, 696 * which has performance implications, e.g. see https://gcc.gnu.org/PR38466 697 */ 698 template<typename _T1, typename _T2> 699 _GLIBCXX20_CONSTEXPR inline 700 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11 701 // Constrained free swap overload, see p0185r1 702 typename enable_if<__and_<__is_swappable<_T1>, 703 __is_swappable<_T2>>::value>::type 704 #else 705 void 706 #endif 707 swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y) 708 noexcept(noexcept(__x.swap(__y))) 709 { __x.swap(__y); } 710 711 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11 712 template<typename _T1, typename _T2> 713 typename enable_if<!__and_<__is_swappable<_T1>, 714 __is_swappable<_T2>>::value>::type 715 swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete; 716 #endif 717 #endif // __cplusplus >= 201103L 718 719 /// @} relates pair 720 721 /** 722 * @brief A convenience wrapper for creating a pair from two objects. 723 * @param __x The first object. 724 * @param __y The second object. 725 * @return A newly-constructed pair<> object of the appropriate type. 726 * 727 * The C++98 standard says the objects are passed by reference-to-const, 728 * but C++03 says they are passed by value (this was LWG issue #181). 729 * 730 * Since C++11 they have been passed by forwarding reference and then 731 * forwarded to the new members of the pair. To create a pair with a 732 * member of reference type, pass a `reference_wrapper` to this function. 733 */ 734 // _GLIBCXX_RESOLVE_LIB_DEFECTS 735 // 181. make_pair() unintended behavior 736 #if __cplusplus >= 201103L 737 // NB: DR 706. 738 template<typename _T1, typename _T2> 739 constexpr pair<typename __decay_and_strip<_T1>::__type, 740 typename __decay_and_strip<_T2>::__type> 741 make_pair(_T1&& __x, _T2&& __y) 742 { 743 typedef typename __decay_and_strip<_T1>::__type __ds_type1; 744 typedef typename __decay_and_strip<_T2>::__type __ds_type2; 745 typedef pair<__ds_type1, __ds_type2> __pair_type; 746 return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y)); 747 } 748 #else 749 template<typename _T1, typename _T2> 750 inline pair<_T1, _T2> 751 make_pair(_T1 __x, _T2 __y) 752 { return pair<_T1, _T2>(__x, __y); } 753 #endif 754 755 /// @} 756 757 #if __cplusplus >= 201103L 758 // Various functions which give std::pair a tuple-like interface. 759 760 template<typename _T1, typename _T2> 761 struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type 762 { }; 763 764 /// Partial specialization for std::pair 765 template<class _Tp1, class _Tp2> 766 struct tuple_size<pair<_Tp1, _Tp2>> 767 : public integral_constant<size_t, 2> { }; 768 769 /// Partial specialization for std::pair 770 template<class _Tp1, class _Tp2> 771 struct tuple_element<0, pair<_Tp1, _Tp2>> 772 { typedef _Tp1 type; }; 773 774 /// Partial specialization for std::pair 775 template<class _Tp1, class _Tp2> 776 struct tuple_element<1, pair<_Tp1, _Tp2>> 777 { typedef _Tp2 type; }; 778 779 #if __cplusplus >= 201703L 780 template<typename _Tp1, typename _Tp2> 781 inline constexpr size_t tuple_size_v<pair<_Tp1, _Tp2>> = 2; 782 783 template<typename _Tp1, typename _Tp2> 784 inline constexpr size_t tuple_size_v<const pair<_Tp1, _Tp2>> = 2; 785 786 template<typename _Tp> 787 inline constexpr bool __is_pair = false; 788 789 template<typename _Tp, typename _Up> 790 inline constexpr bool __is_pair<pair<_Tp, _Up>> = true; 791 792 template<typename _Tp, typename _Up> 793 inline constexpr bool __is_pair<const pair<_Tp, _Up>> = true; 794 #endif 795 796 /// @cond undocumented 797 template<size_t _Int> 798 struct __pair_get; 799 800 template<> 801 struct __pair_get<0> 802 { 803 template<typename _Tp1, typename _Tp2> 804 static constexpr _Tp1& 805 __get(pair<_Tp1, _Tp2>& __pair) noexcept 806 { return __pair.first; } 807 808 template<typename _Tp1, typename _Tp2> 809 static constexpr _Tp1&& 810 __move_get(pair<_Tp1, _Tp2>&& __pair) noexcept 811 { return std::forward<_Tp1>(__pair.first); } 812 813 template<typename _Tp1, typename _Tp2> 814 static constexpr const _Tp1& 815 __const_get(const pair<_Tp1, _Tp2>& __pair) noexcept 816 { return __pair.first; } 817 818 template<typename _Tp1, typename _Tp2> 819 static constexpr const _Tp1&& 820 __const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept 821 { return std::forward<const _Tp1>(__pair.first); } 822 }; 823 824 template<> 825 struct __pair_get<1> 826 { 827 template<typename _Tp1, typename _Tp2> 828 static constexpr _Tp2& 829 __get(pair<_Tp1, _Tp2>& __pair) noexcept 830 { return __pair.second; } 831 832 template<typename _Tp1, typename _Tp2> 833 static constexpr _Tp2&& 834 __move_get(pair<_Tp1, _Tp2>&& __pair) noexcept 835 { return std::forward<_Tp2>(__pair.second); } 836 837 template<typename _Tp1, typename _Tp2> 838 static constexpr const _Tp2& 839 __const_get(const pair<_Tp1, _Tp2>& __pair) noexcept 840 { return __pair.second; } 841 842 template<typename _Tp1, typename _Tp2> 843 static constexpr const _Tp2&& 844 __const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept 845 { return std::forward<const _Tp2>(__pair.second); } 846 }; 847 /// @endcond 848 849 /** @{ 850 * std::get overloads for accessing members of std::pair 851 */ 852 853 template<size_t _Int, class _Tp1, class _Tp2> 854 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type& 855 get(pair<_Tp1, _Tp2>& __in) noexcept 856 { return __pair_get<_Int>::__get(__in); } 857 858 template<size_t _Int, class _Tp1, class _Tp2> 859 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&& 860 get(pair<_Tp1, _Tp2>&& __in) noexcept 861 { return __pair_get<_Int>::__move_get(std::move(__in)); } 862 863 template<size_t _Int, class _Tp1, class _Tp2> 864 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type& 865 get(const pair<_Tp1, _Tp2>& __in) noexcept 866 { return __pair_get<_Int>::__const_get(__in); } 867 868 template<size_t _Int, class _Tp1, class _Tp2> 869 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&& 870 get(const pair<_Tp1, _Tp2>&& __in) noexcept 871 { return __pair_get<_Int>::__const_move_get(std::move(__in)); } 872 873 #if __cplusplus >= 201402L 874 875 #define __cpp_lib_tuples_by_type 201304L 876 877 template <typename _Tp, typename _Up> 878 constexpr _Tp& 879 get(pair<_Tp, _Up>& __p) noexcept 880 { return __p.first; } 881 882 template <typename _Tp, typename _Up> 883 constexpr const _Tp& 884 get(const pair<_Tp, _Up>& __p) noexcept 885 { return __p.first; } 886 887 template <typename _Tp, typename _Up> 888 constexpr _Tp&& 889 get(pair<_Tp, _Up>&& __p) noexcept 890 { return std::move(__p.first); } 891 892 template <typename _Tp, typename _Up> 893 constexpr const _Tp&& 894 get(const pair<_Tp, _Up>&& __p) noexcept 895 { return std::move(__p.first); } 896 897 template <typename _Tp, typename _Up> 898 constexpr _Tp& 899 get(pair<_Up, _Tp>& __p) noexcept 900 { return __p.second; } 901 902 template <typename _Tp, typename _Up> 903 constexpr const _Tp& 904 get(const pair<_Up, _Tp>& __p) noexcept 905 { return __p.second; } 906 907 template <typename _Tp, typename _Up> 908 constexpr _Tp&& 909 get(pair<_Up, _Tp>&& __p) noexcept 910 { return std::move(__p.second); } 911 912 template <typename _Tp, typename _Up> 913 constexpr const _Tp&& 914 get(const pair<_Up, _Tp>&& __p) noexcept 915 { return std::move(__p.second); } 916 917 #endif // C++14 918 /// @} 919 #endif // C++11 920 921 _GLIBCXX_END_NAMESPACE_VERSION 922 } // namespace std 923 924 #endif /* _STL_PAIR_H */ 925