1// <optional> -*- C++ -*- 2 3// Copyright (C) 2013-2014 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/** @file experimental/optional 26 * This is a TS C++ Library header. 27 */ 28 29#ifndef _GLIBCXX_EXPERIMENTAL_OPTIONAL 30#define _GLIBCXX_EXPERIMENTAL_OPTIONAL 1 31 32/** 33 * @defgroup experimental Experimental 34 * 35 * Components specified by various Technical Specifications. 36 */ 37 38#if __cplusplus <= 201103L 39# include <bits/c++14_warning.h> 40#else 41 42#include <utility> 43#include <type_traits> 44#include <stdexcept> 45#include <new> 46#include <initializer_list> 47#include <bits/functexcept.h> 48#include <bits/functional_hash.h> 49#include <bits/enable_special_members.h> 50 51namespace std _GLIBCXX_VISIBILITY(default) 52{ 53namespace experimental 54{ 55_GLIBCXX_BEGIN_NAMESPACE_VERSION 56 57 /** 58 * @defgroup optional Optional values 59 * @ingroup experimental 60 * 61 * Class template for optional values and surrounding facilities, as 62 * described in n3793 "A proposal to add a utility class to represent 63 * optional objects (Revision 5)". 64 * 65 * @{ 66 */ 67 68 // All subsequent [X.Y.n] references are against n3793. 69 70 // [X.Y.4] 71 template<typename _Tp> 72 class optional; 73 74 // [X.Y.5] 75 /// Tag type for in-place construction. 76 struct in_place_t { }; 77 78 /// Tag for in-place construction. 79 constexpr in_place_t in_place { }; 80 81 // [X.Y.6] 82 /// Tag type to disengage optional objects. 83 struct nullopt_t 84 { 85 // Do not user-declare default constructor at all for 86 // optional_value = {} syntax to work. 87 // nullopt_t() = delete; 88 89 // Used for constructing nullopt. 90 enum class _Construct { _Token }; 91 92 // Must be constexpr for nullopt_t to be literal. 93 explicit constexpr nullopt_t(_Construct) { } 94 }; 95 96 // [X.Y.6] 97 /// Tag to disengage optional objects. 98 constexpr nullopt_t nullopt { nullopt_t::_Construct::_Token }; 99 100 // [X.Y.7] 101 /** 102 * @brief Exception class thrown when a disengaged optional object is 103 * dereferenced. 104 * @ingroup exceptions 105 */ 106 class bad_optional_access : public logic_error 107 { 108 public: 109 bad_optional_access() : logic_error("bad optional access") { } 110 111 // XXX This constructor is non-standard. Should not be inline 112 explicit bad_optional_access(const char* __arg) : logic_error(__arg) { } 113 114 virtual ~bad_optional_access() noexcept = default; 115 }; 116 117 void 118 __throw_bad_optional_access(const char*) 119 __attribute__((__noreturn__)); 120 121 // XXX Does not belong here. 122 inline void 123 __throw_bad_optional_access(const char* __s) 124 { _GLIBCXX_THROW_OR_ABORT(bad_optional_access(__s)); } 125 126 template<typename _Tp, typename _Sfinae = void> 127 struct _Has_addressof_impl : std::false_type { }; 128 129 template<typename _Tp> 130 struct _Has_addressof_impl<_Tp, 131 decltype( std::declval<const _Tp&>().operator&(), void() )> 132 : std::true_type { }; 133 134 /** 135 * @brief Trait that detects the presence of an overloaded unary operator&. 136 * 137 * Practically speaking this detects the presence of such an operator when 138 * called on a const-qualified lvalue (i.e. 139 * declval<_Tp * const&>().operator&()). 140 */ 141 template<typename _Tp> 142 struct _Has_addressof : _Has_addressof_impl<_Tp>::type { }; 143 144 /** 145 * @brief An overload that attempts to take the address of an lvalue as a 146 * constant expression. Falls back to __addressof in the presence of an 147 * overloaded addressof operator (unary operator&), in which case the call 148 * will not be a constant expression. 149 */ 150 template<typename _Tp, typename enable_if<!_Has_addressof<_Tp>::value, 151 int>::type...> 152 constexpr _Tp* __constexpr_addressof(_Tp& __t) 153 { return &__t; } 154 155 /** 156 * @brief Fallback overload that defers to __addressof. 157 */ 158 template<typename _Tp, typename enable_if<_Has_addressof<_Tp>::value, 159 int>::type...> 160 inline _Tp* __constexpr_addressof(_Tp& __t) 161 { return std::__addressof(__t); } 162 163 /** 164 * @brief Class template that holds the necessary state for @ref optional 165 * and that has the responsibility for construction and the special members. 166 * 167 * Such a separate base class template is necessary in order to 168 * conditionally enable the special members (e.g. copy/move constructors). 169 * Note that this means that @ref _Optional_base implements the 170 * functionality for copy and move assignment, but not for converting 171 * assignment. 172 * 173 * @see optional, _Enable_special_members 174 */ 175 template<typename _Tp, bool _ShouldProvideDestructor = 176 !is_trivially_destructible<_Tp>::value> 177 class _Optional_base 178 { 179 private: 180 // Remove const to avoid prohibition of reusing object storage for 181 // const-qualified types in [3.8/9]. This is strictly internal 182 // and even optional itself is oblivious to it. 183 using _Stored_type = typename remove_const<_Tp>::type; 184 185 public: 186 // [X.Y.4.1] Constructors. 187 188 // Constructors for disengaged optionals. 189 constexpr _Optional_base() noexcept 190 : _M_empty{} { } 191 192 constexpr _Optional_base(nullopt_t) noexcept 193 : _Optional_base{} { } 194 195 // Constructors for engaged optionals. 196 constexpr _Optional_base(const _Tp& __t) 197 : _M_payload(__t), _M_engaged(true) { } 198 199 constexpr _Optional_base(_Tp&& __t) 200 : _M_payload(std::move(__t)), _M_engaged(true) { } 201 202 template<typename... _Args> 203 constexpr explicit _Optional_base(in_place_t, _Args&&... __args) 204 : _M_payload(std::forward<_Args>(__args)...), _M_engaged(true) { } 205 206 template<typename _Up, typename... _Args, 207 typename enable_if<is_constructible<_Tp, 208 initializer_list<_Up>&, 209 _Args&&...>::value, 210 int>::type...> 211 constexpr explicit _Optional_base(in_place_t, 212 initializer_list<_Up> __il, 213 _Args&&... __args) 214 : _M_payload(__il, std::forward<_Args>(__args)...), 215 _M_engaged(true) { } 216 217 // Copy and move constructors. 218 _Optional_base(const _Optional_base& __other) 219 { 220 if (__other._M_engaged) 221 this->_M_construct(__other._M_get()); 222 } 223 224 _Optional_base(_Optional_base&& __other) 225 noexcept(is_nothrow_move_constructible<_Tp>()) 226 { 227 if (__other._M_engaged) 228 this->_M_construct(std::move(__other._M_get())); 229 } 230 231 // [X.Y.4.3] (partly) Assignment. 232 _Optional_base& 233 operator=(const _Optional_base& __other) 234 { 235 if (this->_M_engaged && __other._M_engaged) 236 this->_M_get() = __other._M_get(); 237 else 238 { 239 if (__other._M_engaged) 240 this->_M_construct(__other._M_get()); 241 else 242 this->_M_reset(); 243 } 244 245 return *this; 246 } 247 248 _Optional_base& 249 operator=(_Optional_base&& __other) 250 noexcept(__and_<is_nothrow_move_constructible<_Tp>, 251 is_nothrow_move_assignable<_Tp>>()) 252 { 253 if (this->_M_engaged && __other._M_engaged) 254 this->_M_get() = std::move(__other._M_get()); 255 else 256 { 257 if (__other._M_engaged) 258 this->_M_construct(std::move(__other._M_get())); 259 else 260 this->_M_reset(); 261 } 262 return *this; 263 } 264 265 // [X.Y.4.2] Destructor. 266 ~_Optional_base() 267 { 268 if (this->_M_engaged) 269 this->_M_payload.~_Stored_type(); 270 } 271 272 // The following functionality is also needed by optional, hence the 273 // protected accessibility. 274 protected: 275 constexpr bool _M_is_engaged() const noexcept 276 { return this->_M_engaged; } 277 278 // The _M_get operations have _M_engaged as a precondition. 279 _Tp& 280 _M_get() noexcept 281 { return _M_payload; } 282 283 constexpr const _Tp& 284 _M_get() const noexcept 285 { return _M_payload; } 286 287 // The _M_construct operation has !_M_engaged as a precondition 288 // while _M_destruct has _M_engaged as a precondition. 289 template<typename... _Args> 290 void 291 _M_construct(_Args&&... __args) 292 noexcept(is_nothrow_constructible<_Stored_type, _Args...>()) 293 { 294 ::new (std::__addressof(this->_M_payload)) 295 _Stored_type(std::forward<_Args>(__args)...); 296 this->_M_engaged = true; 297 } 298 299 void 300 _M_destruct() 301 { 302 this->_M_engaged = false; 303 this->_M_payload.~_Stored_type(); 304 } 305 306 // _M_reset is a 'safe' operation with no precondition. 307 void 308 _M_reset() 309 { 310 if (this->_M_engaged) 311 this->_M_destruct(); 312 } 313 314 private: 315 struct _Empty_byte { }; 316 union { 317 _Empty_byte _M_empty; 318 _Stored_type _M_payload; 319 }; 320 bool _M_engaged = false; 321 }; 322 323 /// Partial specialization that is exactly identical to the primary template 324 /// save for not providing a destructor, to fulfill triviality requirements. 325 template<typename _Tp> 326 class _Optional_base<_Tp, false> 327 { 328 private: 329 using _Stored_type = typename remove_const<_Tp>::type; 330 331 public: 332 constexpr _Optional_base() noexcept 333 : _M_empty{} { } 334 335 constexpr _Optional_base(nullopt_t) noexcept 336 : _Optional_base{} { } 337 338 constexpr _Optional_base(const _Tp& __t) 339 : _M_payload(__t), _M_engaged(true) { } 340 341 constexpr _Optional_base(_Tp&& __t) 342 : _M_payload(std::move(__t)), _M_engaged(true) { } 343 344 template<typename... _Args> 345 constexpr explicit _Optional_base(in_place_t, _Args&&... __args) 346 : _M_payload(std::forward<_Args>(__args)...), _M_engaged(true) { } 347 348 template<typename _Up, typename... _Args, 349 typename enable_if<is_constructible<_Tp, 350 initializer_list<_Up>&, 351 _Args&&...>::value, 352 int>::type...> 353 constexpr explicit _Optional_base(in_place_t, 354 initializer_list<_Up> __il, 355 _Args&&... __args) 356 : _M_payload(__il, std::forward<_Args>(__args)...), 357 _M_engaged(true) { } 358 359 _Optional_base(const _Optional_base& __other) 360 { 361 if (__other._M_engaged) 362 this->_M_construct(__other._M_get()); 363 } 364 365 _Optional_base(_Optional_base&& __other) 366 noexcept(is_nothrow_move_constructible<_Tp>()) 367 { 368 if (__other._M_engaged) 369 this->_M_construct(std::move(__other._M_get())); 370 } 371 372 _Optional_base& 373 operator=(const _Optional_base& __other) 374 { 375 if (this->_M_engaged && __other._M_engaged) 376 this->_M_get() = __other._M_get(); 377 else 378 { 379 if (__other._M_engaged) 380 this->_M_construct(__other._M_get()); 381 else 382 this->_M_reset(); 383 } 384 return *this; 385 } 386 387 _Optional_base& 388 operator=(_Optional_base&& __other) 389 noexcept(__and_<is_nothrow_move_constructible<_Tp>, 390 is_nothrow_move_assignable<_Tp>>()) 391 { 392 if (this->_M_engaged && __other._M_engaged) 393 this->_M_get() = std::move(__other._M_get()); 394 else 395 { 396 if (__other._M_engaged) 397 this->_M_construct(std::move(__other._M_get())); 398 else 399 this->_M_reset(); 400 } 401 return *this; 402 } 403 404 // Sole difference 405 // ~_Optional_base() noexcept = default; 406 407 protected: 408 constexpr bool _M_is_engaged() const noexcept 409 { return this->_M_engaged; } 410 411 _Tp& 412 _M_get() noexcept 413 { return _M_payload; } 414 415 constexpr const _Tp& 416 _M_get() const noexcept 417 { return _M_payload; } 418 419 template<typename... _Args> 420 void 421 _M_construct(_Args&&... __args) 422 noexcept(is_nothrow_constructible<_Stored_type, _Args...>()) 423 { 424 ::new (std::__addressof(this->_M_payload)) 425 _Stored_type(std::forward<_Args>(__args)...); 426 this->_M_engaged = true; 427 } 428 429 void 430 _M_destruct() 431 { 432 this->_M_engaged = false; 433 this->_M_payload.~_Stored_type(); 434 } 435 436 void 437 _M_reset() 438 { 439 if (this->_M_engaged) 440 this->_M_destruct(); 441 } 442 443 private: 444 struct _Empty_byte { }; 445 union 446 { 447 _Empty_byte _M_empty; 448 _Stored_type _M_payload; 449 }; 450 bool _M_engaged = false; 451 }; 452 453 /** 454 * @brief Class template for optional values. 455 */ 456 template<typename _Tp> 457 class optional 458 : private _Optional_base<_Tp>, 459 private _Enable_copy_move< 460 // Copy constructor. 461 is_copy_constructible<_Tp>::value, 462 // Copy assignment. 463 __and_<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>::value, 464 // Move constructor. 465 is_move_constructible<_Tp>::value, 466 // Move assignment. 467 __and_<is_move_constructible<_Tp>, is_move_assignable<_Tp>>::value, 468 // Unique tag type. 469 optional<_Tp>> 470 { 471 static_assert(__and_<__not_<is_same<typename remove_cv<_Tp>::type, 472 nullopt_t>>, 473 __not_<is_same<typename remove_cv<_Tp>::type, 474 in_place_t>>, 475 __not_<is_reference<_Tp>>>(), 476 "Invalid instantiation of optional<T>"); 477 478 private: 479 using _Base = _Optional_base<_Tp>; 480 481 public: 482 using value_type = _Tp; 483 484 // _Optional_base has the responsibility for construction. 485 using _Base::_Base; 486 487 // [X.Y.4.3] (partly) Assignment. 488 optional& 489 operator=(nullopt_t) noexcept 490 { 491 this->_M_reset(); 492 return *this; 493 } 494 495 template<typename _Up> 496 typename enable_if< 497 is_same<_Tp, typename decay<_Up>::type>::value, 498 optional& 499 >::type 500 operator=(_Up&& __u) 501 { 502 static_assert(__and_<is_constructible<_Tp, _Up>, 503 is_assignable<_Tp&, _Up>>(), 504 "Cannot assign to value type from argument"); 505 506 if (this->_M_is_engaged()) 507 this->_M_get() = std::forward<_Up>(__u); 508 else 509 this->_M_construct(std::forward<_Up>(__u)); 510 511 return *this; 512 } 513 514 template<typename... _Args> 515 void 516 emplace(_Args&&... __args) 517 { 518 static_assert(is_constructible<_Tp, _Args&&...>(), 519 "Cannot emplace value type from arguments"); 520 521 this->_M_reset(); 522 this->_M_construct(std::forward<_Args>(__args)...); 523 } 524 525 template<typename _Up, typename... _Args> 526 typename enable_if< 527 is_constructible<_Tp, 528 initializer_list<_Up>&, 529 _Args&&...>::value 530 >::type 531 emplace(initializer_list<_Up> __il, _Args&&... __args) 532 { 533 this->_M_reset(); 534 this->_M_construct(__il, std::forward<_Args>(__args)...); 535 } 536 537 // [X.Y.4.2] Destructor is implicit, implemented in _Optional_base. 538 539 // [X.Y.4.4] Swap. 540 void 541 swap(optional& __other) 542 noexcept(is_nothrow_move_constructible<_Tp>() 543 && noexcept(swap(declval<_Tp&>(), declval<_Tp&>()))) 544 { 545 using std::swap; 546 547 if (this->_M_is_engaged() && __other._M_is_engaged()) 548 swap(this->_M_get(), __other._M_get()); 549 else if (this->_M_is_engaged()) 550 { 551 __other._M_construct(std::move(this->_M_get())); 552 this->_M_destruct(); 553 } 554 else if (__other._M_is_engaged()) 555 { 556 this->_M_construct(std::move(__other._M_get())); 557 __other._M_destruct(); 558 } 559 } 560 561 // [X.Y.4.5] Observers. 562 constexpr const _Tp* 563 operator->() const 564 { return __constexpr_addressof(this->_M_get()); } 565 566 _Tp* 567 operator->() 568 { return std::__addressof(this->_M_get()); } 569 570 constexpr const _Tp& 571 operator*() const 572 { return this->_M_get(); } 573 574 _Tp& 575 operator*() 576 { return this->_M_get(); } 577 578 constexpr explicit operator bool() const noexcept 579 { return this->_M_is_engaged(); } 580 581 constexpr const _Tp& 582 value() const 583 { 584 return this->_M_is_engaged() 585 ? this->_M_get() 586 : (__throw_bad_optional_access("Attempt to access value of a " 587 "disengaged optional object"), 588 this->_M_get()); 589 } 590 591 _Tp& 592 value() 593 { 594 if (this->_M_is_engaged()) 595 return this->_M_get(); 596 597 __throw_bad_optional_access("Attempt to access value of a " 598 "disengaged optional object"); 599 } 600 601 template<typename _Up> 602 constexpr _Tp 603 value_or(_Up&& __u) const& 604 { 605 static_assert(__and_<is_copy_constructible<_Tp>, 606 is_convertible<_Up&&, _Tp>>(), 607 "Cannot return value"); 608 609 return this->_M_is_engaged() 610 ? this->_M_get() 611 : static_cast<_Tp>(std::forward<_Up>(__u)); 612 } 613 614 template<typename _Up> 615 _Tp 616 value_or(_Up&& __u) && 617 { 618 static_assert(__and_<is_move_constructible<_Tp>, 619 is_convertible<_Up&&, _Tp>>(), 620 "Cannot return value" ); 621 622 return this->_M_is_engaged() 623 ? std::move(this->_M_get()) 624 : static_cast<_Tp>(std::forward<_Up>(__u)); 625 } 626 }; 627 628 // [X.Y.8] Comparisons between optional values. 629 template<typename _Tp> 630 constexpr bool 631 operator==(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 632 { 633 return static_cast<bool>(__lhs) == static_cast<bool>(__rhs) 634 && (!__lhs || *__lhs == *__rhs); 635 } 636 637 template<typename _Tp> 638 constexpr bool 639 operator!=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 640 { return !(__lhs == __rhs); } 641 642 template<typename _Tp> 643 constexpr bool 644 operator<(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 645 { 646 return static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs); 647 } 648 649 template<typename _Tp> 650 constexpr bool 651 operator>(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 652 { return __rhs < __lhs; } 653 654 template<typename _Tp> 655 constexpr bool 656 operator<=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 657 { return !(__rhs < __lhs); } 658 659 template<typename _Tp> 660 constexpr bool 661 operator>=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs) 662 { return !(__lhs < __rhs); } 663 664 // [X.Y.9] Comparisons with nullopt. 665 template<typename _Tp> 666 constexpr bool 667 operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept 668 { return !__lhs; } 669 670 template<typename _Tp> 671 constexpr bool 672 operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept 673 { return !__rhs; } 674 675 template<typename _Tp> 676 constexpr bool 677 operator!=(const optional<_Tp>& __lhs, nullopt_t) noexcept 678 { return static_cast<bool>(__lhs); } 679 680 template<typename _Tp> 681 constexpr bool 682 operator!=(nullopt_t, const optional<_Tp>& __rhs) noexcept 683 { return static_cast<bool>(__rhs); } 684 685 template<typename _Tp> 686 constexpr bool 687 operator<(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept 688 { return false; } 689 690 template<typename _Tp> 691 constexpr bool 692 operator<(nullopt_t, const optional<_Tp>& __rhs) noexcept 693 { return static_cast<bool>(__rhs); } 694 695 template<typename _Tp> 696 constexpr bool 697 operator>(const optional<_Tp>& __lhs, nullopt_t) noexcept 698 { return static_cast<bool>(__lhs); } 699 700 template<typename _Tp> 701 constexpr bool 702 operator>(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept 703 { return false; } 704 705 template<typename _Tp> 706 constexpr bool 707 operator<=(const optional<_Tp>& __lhs, nullopt_t) noexcept 708 { return !__lhs; } 709 710 template<typename _Tp> 711 constexpr bool 712 operator<=(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept 713 { return true; } 714 715 template<typename _Tp> 716 constexpr bool 717 operator>=(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept 718 { return true; } 719 720 template<typename _Tp> 721 constexpr bool 722 operator>=(nullopt_t, const optional<_Tp>& __rhs) noexcept 723 { return !__rhs; } 724 725 // [X.Y.10] Comparisons with value type. 726 template<typename _Tp> 727 constexpr bool 728 operator==(const optional<_Tp>& __lhs, const _Tp& __rhs) 729 { return __lhs && *__lhs == __rhs; } 730 731 template<typename _Tp> 732 constexpr bool 733 operator==(const _Tp& __lhs, const optional<_Tp>& __rhs) 734 { return __rhs && __lhs == *__rhs; } 735 736 template<typename _Tp> 737 constexpr bool 738 operator!=(const optional<_Tp>& __lhs, _Tp const& __rhs) 739 { return !__lhs || !(*__lhs == __rhs); } 740 741 template<typename _Tp> 742 constexpr bool 743 operator!=(const _Tp& __lhs, const optional<_Tp>& __rhs) 744 { return !__rhs || !(__lhs == *__rhs); } 745 746 template<typename _Tp> 747 constexpr bool 748 operator<(const optional<_Tp>& __lhs, const _Tp& __rhs) 749 { return !__lhs || *__lhs < __rhs; } 750 751 template<typename _Tp> 752 constexpr bool 753 operator<(const _Tp& __lhs, const optional<_Tp>& __rhs) 754 { return __rhs && __lhs < *__rhs; } 755 756 template<typename _Tp> 757 constexpr bool 758 operator>(const optional<_Tp>& __lhs, const _Tp& __rhs) 759 { return __lhs && __rhs < *__lhs; } 760 761 template<typename _Tp> 762 constexpr bool 763 operator>(const _Tp& __lhs, const optional<_Tp>& __rhs) 764 { return !__rhs || *__rhs < __lhs; } 765 766 template<typename _Tp> 767 constexpr bool 768 operator<=(const optional<_Tp>& __lhs, const _Tp& __rhs) 769 { return !__lhs || !(__rhs < *__lhs); } 770 771 template<typename _Tp> 772 constexpr bool 773 operator<=(const _Tp& __lhs, const optional<_Tp>& __rhs) 774 { return __rhs && !(*__rhs < __lhs); } 775 776 template<typename _Tp> 777 constexpr bool 778 operator>=(const optional<_Tp>& __lhs, const _Tp& __rhs) 779 { return __lhs && !(*__lhs < __rhs); } 780 781 template<typename _Tp> 782 constexpr bool 783 operator>=(const _Tp& __lhs, const optional<_Tp>& __rhs) 784 { return !__rhs || !(__lhs < *__rhs); } 785 786 // [X.Y.11] 787 template<typename _Tp> 788 inline void 789 swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs) 790 noexcept(noexcept(__lhs.swap(__rhs))) 791 { __lhs.swap(__rhs); } 792 793 template<typename _Tp> 794 constexpr optional<typename decay<_Tp>::type> 795 make_optional(_Tp&& __t) 796 { return optional<typename decay<_Tp>::type> { std::forward<_Tp>(__t) }; } 797 798 // @} group optional 799_GLIBCXX_END_NAMESPACE_VERSION 800} 801 802 // [X.Y.12] 803 template<typename _Tp> 804 struct hash<experimental::optional<_Tp>> 805 { 806 using result_type = size_t; 807 using argument_type = experimental::optional<_Tp>; 808 809 size_t 810 operator()(const experimental::optional<_Tp>& __t) const 811 noexcept(noexcept(hash<_Tp> {}(*__t))) 812 { 813 // We pick an arbitrary hash for disengaged optionals which hopefully 814 // usual values of _Tp won't typically hash to. 815 constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333); 816 return __t ? hash<_Tp> {}(*__t) : __magic_disengaged_hash; 817 } 818 }; 819} 820 821#endif // C++14 822 823#endif // _GLIBCXX_EXPERIMENTAL_OPTIONAL 824