boost/tuple/detail/tuple_basic.hpp

   1 //  tuple_basic.hpp -----------------------------------------------------
   2
   3 // Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
   4 //
   5 // Distributed under the Boost Software License, Version 1.0. (See
   6 // accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8
   9 // For more information, see http://www.boost.org
  10
  11 // Outside help:
  12 // This and that, Gary Powell.
  13 // Fixed return types for get_head/get_tail
  14 // ( and other bugs ) per suggestion of Jens Maurer
  15 // simplified element type accessors + bug fix  (Jeremy Siek)
  16 // Several changes/additions according to suggestions by Douglas Gregor,
  17 // William Kempf, Vesa Karvonen, John Max Skaller, Ed Brey, Beman Dawes,
  18 // David Abrahams.
  19
  20 // Revision history:
  21 // 2002 05 01 Hugo Duncan: Fix for Borland after Jaakko's previous changes
  22 // 2002 04 18 Jaakko: tuple element types can be void or plain function
  23 //                    types, as long as no object is created.
  24 //                    Tuple objects can no hold even noncopyable types
  25 //                    such as arrays.
  26 // 2001 10 22 John Maddock
  27 //      Fixes for Borland C++
  28 // 2001 08 30 David Abrahams
  29 //      Added default constructor for cons<>.
  30 // -----------------------------------------------------------------
  31
  32 #ifndef BOOST_TUPLE_BASIC_HPP
  33 #define BOOST_TUPLE_BASIC_HPP
  34
  35
  36 #include <utility> // needed for the assignment from pair to tuple
  37
  38 #include "boost/type_traits/cv_traits.hpp"
  39 #include "boost/type_traits/function_traits.hpp"
  40
  41 #include "boost/detail/workaround.hpp" // needed for BOOST_WORKAROUND
  42
  43 namespace boost {
  44 namespace tuples {
  45
  46 // -- null_type --------------------------------------------------------
  47 struct null_type {};
  48
  49 // a helper function to provide a const null_type type temporary
  50 namespace detail {
  51   inline const null_type cnull() { return null_type(); }
  52
  53
  54 // -- if construct ------------------------------------------------
  55 // Proposed by Krzysztof Czarnecki and Ulrich Eisenecker
  56
  57 template <bool If, class Then, class Else> struct IF { typedef Then RET; };
  58
  59 template <class Then, class Else> struct IF<false, Then, Else> {
  60   typedef Else RET;
  61 };
  62
  63 } // end detail
  64
  65 // - cons forward declaration -----------------------------------------------
  66 template <class HT, class TT> struct cons;
  67
  68
  69 // - tuple forward declaration -----------------------------------------------
  70 template <
  71   class T0 = null_type, class T1 = null_type, class T2 = null_type,
  72   class T3 = null_type, class T4 = null_type, class T5 = null_type,
  73   class T6 = null_type, class T7 = null_type, class T8 = null_type,
  74   class T9 = null_type>
  75 class tuple;
  76
  77 // tuple_length forward declaration
  78 template<class T> struct length;
  79
  80
  81
  82 namespace detail {
  83
  84 // -- generate error template, referencing to non-existing members of this
  85 // template is used to produce compilation errors intentionally
  86 template<class T>
  87 class generate_error;
  88
  89 // - cons getters --------------------------------------------------------
  90 // called: get_class<N>::get<RETURN_TYPE>(aTuple)
  91
  92 template< int N >
  93 struct get_class {
  94   template<class RET, class HT, class TT >
  95   inline static RET get(const cons<HT, TT>& t)
  96   {
  97 #if BOOST_WORKAROUND(__IBMCPP__,==600)
  98     // vacpp 6.0 is not very consistent regarding the member template keyword
  99     // Here it generates an error when the template keyword is used.
 100     return get_class<N-1>::get<RET>(t.tail);
 101 #else
 102     return get_class<N-1>::BOOST_NESTED_TEMPLATE get<RET>(t.tail);
 103 #endif
 104   }
 105   template<class RET, class HT, class TT >
 106   inline static RET get(cons<HT, TT>& t)
 107   {
 108 #if BOOST_WORKAROUND(__IBMCPP__,==600)
 109     return get_class<N-1>::get<RET>(t.tail);
 110 #else
 111     return get_class<N-1>::BOOST_NESTED_TEMPLATE get<RET>(t.tail);
 112 #endif
 113   }
 114 };
 115
 116 template<>
 117 struct get_class<0> {
 118   template<class RET, class HT, class TT>
 119   inline static RET get(const cons<HT, TT>& t)
 120   {
 121     return t.head;
 122   }
 123   template<class RET, class HT, class TT>
 124   inline static RET get(cons<HT, TT>& t)
 125   {
 126     return t.head;
 127   }
 128 };
 129
 130 } // end of namespace detail
 131
 132
 133 // -cons type accessors ----------------------------------------
 134 // typename tuples::element<N,T>::type gets the type of the
 135 // Nth element ot T, first element is at index 0
 136 // -------------------------------------------------------
 137
 138 #ifndef BOOST_NO_CV_SPECIALIZATIONS
 139
 140 template<int N, class T>
 141 struct element
 142 {
 143 private:
 144   typedef typename T::tail_type Next;
 145 public:
 146   typedef typename element<N-1, Next>::type type;
 147 };
 148 template<class T>
 149 struct element<0,T>
 150 {
 151   typedef typename T::head_type type;
 152 };
 153
 154 template<int N, class T>
 155 struct element<N, const T>
 156 {
 157 private:
 158   typedef typename T::tail_type Next;
 159   typedef typename element<N-1, Next>::type unqualified_type;
 160 public:
 161 #if BOOST_WORKAROUND(__BORLANDC__,<0x600)
 162   typedef const unqualified_type type;
 163 #else
 164   typedef typename boost::add_const<unqualified_type>::type type;
 165 #endif
 166
 167 };
 168 template<class T>
 169 struct element<0,const T>
 170 {
 171 #if BOOST_WORKAROUND(__BORLANDC__,<0x600)
 172   typedef const typename T::head_type type;
 173 #else
 174   typedef typename boost::add_const<typename T::head_type>::type type;
 175 #endif
 176 };
 177
 178 #else // def BOOST_NO_CV_SPECIALIZATIONS
 179
 180 namespace detail {
 181
 182 template<int N, class T, bool IsConst>
 183 struct element_impl
 184 {
 185 private:
 186   typedef typename T::tail_type Next;
 187 public:
 188   typedef typename element_impl<N-1, Next, IsConst>::type type;
 189 };
 190
 191 template<int N, class T>
 192 struct element_impl<N, T, true /* IsConst */>
 193 {
 194 private:
 195   typedef typename T::tail_type Next;
 196 public:
 197   typedef const typename element_impl<N-1, Next, true>::type type;
 198 };
 199
 200 template<class T>
 201 struct element_impl<0, T, false /* IsConst */>
 202 {
 203   typedef typename T::head_type type;
 204 };
 205
 206 template<class T>
 207 struct element_impl<0, T, true /* IsConst */>
 208 {
 209   typedef const typename T::head_type type;
 210 };
 211
 212 } // end of namespace detail
 213
 214
 215 template<int N, class T>
 216 struct element:
 217   public detail::element_impl<N, T, ::boost::is_const<T>::value>
 218 {
 219 };
 220
 221 #endif
 222
 223
 224 // -get function templates -----------------------------------------------
 225 // Usage: get<N>(aTuple)
 226
 227 // -- some traits classes for get functions
 228
 229 // access traits lifted from detail namespace to be part of the interface,
 230 // (Joel de Guzman's suggestion). Rationale: get functions are part of the
 231 // interface, so should the way to express their return types be.
 232
 233 template <class T> struct access_traits {
 234   typedef const T& const_type;
 235   typedef T& non_const_type;
 236
 237   typedef const typename boost::remove_cv<T>::type& parameter_type;
 238
 239 // used as the tuple constructors parameter types
 240 // Rationale: non-reference tuple element types can be cv-qualified.
 241 // It should be possible to initialize such types with temporaries,
 242 // and when binding temporaries to references, the reference must
 243 // be non-volatile and const. 8.5.3. (5)
 244 };
 245
 246 template <class T> struct access_traits<T&> {
 247
 248   typedef T& const_type;
 249   typedef T& non_const_type;
 250
 251   typedef T& parameter_type;
 252 };
 253
 254 // get function for non-const cons-lists, returns a reference to the element
 255
 256 template<int N, class HT, class TT>
 257 inline typename access_traits<
 258                   typename element<N, cons<HT, TT> >::type
 259                 >::non_const_type
 260 get(cons<HT, TT>& c BOOST_APPEND_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) {
 261 #if BOOST_WORKAROUND(__IBMCPP__,==600 )
 262   return detail::get_class<N>::
 263 #else
 264   return detail::get_class<N>::BOOST_NESTED_TEMPLATE
 265 #endif
 266          get<
 267            typename access_traits<
 268              typename element<N, cons<HT, TT> >::type
 269            >::non_const_type,
 270            HT,TT
 271          >(c);
 272 }
 273
 274 // get function for const cons-lists, returns a const reference to
 275 // the element. If the element is a reference, returns the reference
 276 // as such (that is, can return a non-const reference)
 277 template<int N, class HT, class TT>
 278 inline typename access_traits<
 279                   typename element<N, cons<HT, TT> >::type
 280                 >::const_type
 281 get(const cons<HT, TT>& c BOOST_APPEND_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) {
 282 #if BOOST_WORKAROUND(__IBMCPP__,==600)
 283   return detail::get_class<N>::
 284 #else
 285   return detail::get_class<N>::BOOST_NESTED_TEMPLATE
 286 #endif
 287          get<
 288            typename access_traits<
 289              typename element<N, cons<HT, TT> >::type
 290            >::const_type,
 291            HT,TT
 292          >(c);
 293 }
 294
 295 // -- the cons template  --------------------------------------------------
 296 namespace detail {
 297
 298 //  These helper templates wrap void types and plain function types.
 299 //  The reationale is to allow one to write tuple types with those types
 300 //  as elements, even though it is not possible to instantiate such object.
 301 //  E.g: typedef tuple<void> some_type; // ok
 302 //  but: some_type x; // fails
 303
 304 template <class T> class non_storeable_type {
 305   non_storeable_type();
 306 };
 307
 308 template <class T> struct wrap_non_storeable_type {
 309   typedef typename IF<
 310     ::boost::is_function<T>::value, non_storeable_type<T>, T
 311   >::RET type;
 312 };
 313 template <> struct wrap_non_storeable_type<void> {
 314   typedef non_storeable_type<void> type;
 315 };
 316
 317 } // detail
 318
 319 template <class HT, class TT>
 320 struct cons {
 321
 322   typedef HT head_type;
 323   typedef TT tail_type;
 324
 325   typedef typename
 326     detail::wrap_non_storeable_type<head_type>::type stored_head_type;
 327
 328   stored_head_type head;
 329   tail_type tail;
 330
 331   typename access_traits<stored_head_type>::non_const_type
 332   get_head() { return head; }
 333
 334   typename access_traits<tail_type>::non_const_type
 335   get_tail() { return tail; }
 336
 337   typename access_traits<stored_head_type>::const_type
 338   get_head() const { return head; }
 339
 340   typename access_traits<tail_type>::const_type
 341   get_tail() const { return tail; }
 342
 343   cons() : head(), tail() {}
 344   //  cons() : head(detail::default_arg<HT>::f()), tail() {}
 345
 346   // the argument for head is not strictly needed, but it prevents
 347   // array type elements. This is good, since array type elements
 348   // cannot be supported properly in any case (no assignment,
 349   // copy works only if the tails are exactly the same type, ...)
 350
 351   cons(typename access_traits<stored_head_type>::parameter_type h,
 352        const tail_type& t)
 353     : head (h), tail(t) {}
 354
 355   template <class T1, class T2, class T3, class T4, class T5,
 356             class T6, class T7, class T8, class T9, class T10>
 357   cons( T1& t1, T2& t2, T3& t3, T4& t4, T5& t5,
 358         T6& t6, T7& t7, T8& t8, T9& t9, T10& t10 )
 359     : head (t1),
 360       tail (t2, t3, t4, t5, t6, t7, t8, t9, t10, detail::cnull())
 361       {}
 362
 363   template <class T2, class T3, class T4, class T5,
 364             class T6, class T7, class T8, class T9, class T10>
 365   cons( const null_type& /*t1*/, T2& t2, T3& t3, T4& t4, T5& t5,
 366         T6& t6, T7& t7, T8& t8, T9& t9, T10& t10 )
 367     : head (),
 368       tail (t2, t3, t4, t5, t6, t7, t8, t9, t10, detail::cnull())
 369       {}
 370
 371
 372   template <class HT2, class TT2>
 373   cons( const cons<HT2, TT2>& u ) : head(u.head), tail(u.tail) {}
 374
 375   template <class HT2, class TT2>
 376   cons& operator=( const cons<HT2, TT2>& u ) {
 377     head=u.head; tail=u.tail; return *this;
 378   }
 379
 380   // must define assignment operator explicitly, implicit version is
 381   // illformed if HT is a reference (12.8. (12))
 382   cons& operator=(const cons& u) {
 383     head = u.head; tail = u.tail;  return *this;
 384   }
 385
 386   template <class T1, class T2>
 387   cons& operator=( const std::pair<T1, T2>& u ) {
 388     BOOST_STATIC_ASSERT(length<cons>::value == 2); // check length = 2
 389     head = u.first; tail.head = u.second; return *this;
 390   }
 391
 392   // get member functions (non-const and const)
 393   template <int N>
 394   typename access_traits<
 395              typename element<N, cons<HT, TT> >::type
 396            >::non_const_type
 397   get() {
 398     return boost::tuples::get<N>(*this); // delegate to non-member get
 399   }
 400
 401   template <int N>
 402   typename access_traits<
 403              typename element<N, cons<HT, TT> >::type
 404            >::const_type
 405   get() const {
 406     return boost::tuples::get<N>(*this); // delegate to non-member get
 407   }
 408 };
 409
 410 template <class HT>
 411 struct cons<HT, null_type> {
 412
 413   typedef HT head_type;
 414   typedef null_type tail_type;
 415   typedef cons<HT, null_type> self_type;
 416
 417   typedef typename
 418     detail::wrap_non_storeable_type<head_type>::type stored_head_type;
 419   stored_head_type head;
 420
 421   typename access_traits<stored_head_type>::non_const_type
 422   get_head() { return head; }
 423
 424   null_type get_tail() { return null_type(); }
 425
 426   typename access_traits<stored_head_type>::const_type
 427   get_head() const { return head; }
 428
 429   const null_type get_tail() const { return null_type(); }
 430
 431   //  cons() : head(detail::default_arg<HT>::f()) {}
 432   cons() : head() {}
 433
 434   cons(typename access_traits<stored_head_type>::parameter_type h,
 435        const null_type& = null_type())
 436     : head (h) {}
 437
 438   template<class T1>
 439   cons(T1& t1, const null_type&, const null_type&, const null_type&,
 440        const null_type&, const null_type&, const null_type&,
 441        const null_type&, const null_type&, const null_type&)
 442   : head (t1) {}
 443
 444   cons(const null_type&,
 445        const null_type&, const null_type&, const null_type&,
 446        const null_type&, const null_type&, const null_type&,
 447        const null_type&, const null_type&, const null_type&)
 448   : head () {}
 449
 450   template <class HT2>
 451   cons( const cons<HT2, null_type>& u ) : head(u.head) {}
 452
 453   template <class HT2>
 454   cons& operator=(const cons<HT2, null_type>& u )
 455   { head = u.head; return *this; }
 456
 457   // must define assignment operator explicitely, implicit version
 458   // is illformed if HT is a reference
 459   cons& operator=(const cons& u) { head = u.head; return *this; }
 460
 461   template <int N>
 462   typename access_traits<
 463              typename element<N, self_type>::type
 464             >::non_const_type
 465   get(BOOST_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) {
 466     return boost::tuples::get<N>(*this);
 467   }
 468
 469   template <int N>
 470   typename access_traits<
 471              typename element<N, self_type>::type
 472            >::const_type
 473   get(BOOST_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) const {
 474     return boost::tuples::get<N>(*this);
 475   }
 476
 477 };
 478
 479 // templates for finding out the length of the tuple -------------------
 480
 481 template<class T>
 482 struct length  {
 483   BOOST_STATIC_CONSTANT(int, value = 1 + length<typename T::tail_type>::value);
 484 };
 485
 486 template<>
 487 struct length<tuple<> > {
 488   BOOST_STATIC_CONSTANT(int, value = 0);
 489 };
 490
 491 template<>
 492 struct length<tuple<> const> {
 493   BOOST_STATIC_CONSTANT(int, value = 0);
 494 };
 495
 496 template<>
 497 struct length<null_type> {
 498   BOOST_STATIC_CONSTANT(int, value = 0);
 499 };
 500
 501 template<>
 502 struct length<null_type const> {
 503   BOOST_STATIC_CONSTANT(int, value = 0);
 504 };
 505
 506 namespace detail {
 507
 508 // Tuple to cons mapper --------------------------------------------------
 509 template <class T0, class T1, class T2, class T3, class T4,
 510           class T5, class T6, class T7, class T8, class T9>
 511 struct map_tuple_to_cons
 512 {
 513   typedef cons<T0,
 514                typename map_tuple_to_cons<T1, T2, T3, T4, T5,
 515                                           T6, T7, T8, T9, null_type>::type
 516               > type;
 517 };
 518
 519 // The empty tuple is a null_type
 520 template <>
 521 struct map_tuple_to_cons<null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type>
 522 {
 523   typedef null_type type;
 524 };
 525
 526 } // end detail
 527
 528 // -------------------------------------------------------------------
 529 // -- tuple ------------------------------------------------------
 530 template <class T0, class T1, class T2, class T3, class T4,
 531           class T5, class T6, class T7, class T8, class T9>
 532
 533 class tuple :
 534   public detail::map_tuple_to_cons<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::type
 535 {
 536 public:
 537   typedef typename
 538     detail::map_tuple_to_cons<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::type inherited;
 539   typedef typename inherited::head_type head_type;
 540   typedef typename inherited::tail_type tail_type;
 541
 542
 543 // access_traits<T>::parameter_type takes non-reference types as const T&
 544   tuple() {}
 545
 546   tuple(typename access_traits<T0>::parameter_type t0)
 547     : inherited(t0, detail::cnull(), detail::cnull(), detail::cnull(),
 548                 detail::cnull(), detail::cnull(), detail::cnull(),
 549                 detail::cnull(), detail::cnull(), detail::cnull()) {}
 550
 551   tuple(typename access_traits<T0>::parameter_type t0,
 552         typename access_traits<T1>::parameter_type t1)
 553     : inherited(t0, t1, detail::cnull(), detail::cnull(),
 554                 detail::cnull(), detail::cnull(), detail::cnull(),
 555                 detail::cnull(), detail::cnull(), detail::cnull()) {}
 556
 557   tuple(typename access_traits<T0>::parameter_type t0,
 558         typename access_traits<T1>::parameter_type t1,
 559         typename access_traits<T2>::parameter_type t2)
 560     : inherited(t0, t1, t2, detail::cnull(), detail::cnull(),
 561                 detail::cnull(), detail::cnull(), detail::cnull(),
 562                 detail::cnull(), detail::cnull()) {}
 563
 564   tuple(typename access_traits<T0>::parameter_type t0,
 565         typename access_traits<T1>::parameter_type t1,
 566         typename access_traits<T2>::parameter_type t2,
 567         typename access_traits<T3>::parameter_type t3)
 568     : inherited(t0, t1, t2, t3, detail::cnull(), detail::cnull(),
 569                 detail::cnull(), detail::cnull(), detail::cnull(),
 570                 detail::cnull()) {}
 571
 572   tuple(typename access_traits<T0>::parameter_type t0,
 573         typename access_traits<T1>::parameter_type t1,
 574         typename access_traits<T2>::parameter_type t2,
 575         typename access_traits<T3>::parameter_type t3,
 576         typename access_traits<T4>::parameter_type t4)
 577     : inherited(t0, t1, t2, t3, t4, detail::cnull(), detail::cnull(),
 578                 detail::cnull(), detail::cnull(), detail::cnull()) {}
 579
 580   tuple(typename access_traits<T0>::parameter_type t0,
 581         typename access_traits<T1>::parameter_type t1,
 582         typename access_traits<T2>::parameter_type t2,
 583         typename access_traits<T3>::parameter_type t3,
 584         typename access_traits<T4>::parameter_type t4,
 585         typename access_traits<T5>::parameter_type t5)
 586     : inherited(t0, t1, t2, t3, t4, t5, detail::cnull(), detail::cnull(),
 587                 detail::cnull(), detail::cnull()) {}
 588
 589   tuple(typename access_traits<T0>::parameter_type t0,
 590         typename access_traits<T1>::parameter_type t1,
 591         typename access_traits<T2>::parameter_type t2,
 592         typename access_traits<T3>::parameter_type t3,
 593         typename access_traits<T4>::parameter_type t4,
 594         typename access_traits<T5>::parameter_type t5,
 595         typename access_traits<T6>::parameter_type t6)
 596     : inherited(t0, t1, t2, t3, t4, t5, t6, detail::cnull(),
 597                 detail::cnull(), detail::cnull()) {}
 598
 599   tuple(typename access_traits<T0>::parameter_type t0,
 600         typename access_traits<T1>::parameter_type t1,
 601         typename access_traits<T2>::parameter_type t2,
 602         typename access_traits<T3>::parameter_type t3,
 603         typename access_traits<T4>::parameter_type t4,
 604         typename access_traits<T5>::parameter_type t5,
 605         typename access_traits<T6>::parameter_type t6,
 606         typename access_traits<T7>::parameter_type t7)
 607     : inherited(t0, t1, t2, t3, t4, t5, t6, t7, detail::cnull(),
 608                 detail::cnull()) {}
 609
 610   tuple(typename access_traits<T0>::parameter_type t0,
 611         typename access_traits<T1>::parameter_type t1,
 612         typename access_traits<T2>::parameter_type t2,
 613         typename access_traits<T3>::parameter_type t3,
 614         typename access_traits<T4>::parameter_type t4,
 615         typename access_traits<T5>::parameter_type t5,
 616         typename access_traits<T6>::parameter_type t6,
 617         typename access_traits<T7>::parameter_type t7,
 618         typename access_traits<T8>::parameter_type t8)
 619     : inherited(t0, t1, t2, t3, t4, t5, t6, t7, t8, detail::cnull()) {}
 620
 621   tuple(typename access_traits<T0>::parameter_type t0,
 622         typename access_traits<T1>::parameter_type t1,
 623         typename access_traits<T2>::parameter_type t2,
 624         typename access_traits<T3>::parameter_type t3,
 625         typename access_traits<T4>::parameter_type t4,
 626         typename access_traits<T5>::parameter_type t5,
 627         typename access_traits<T6>::parameter_type t6,
 628         typename access_traits<T7>::parameter_type t7,
 629         typename access_traits<T8>::parameter_type t8,
 630         typename access_traits<T9>::parameter_type t9)
 631     : inherited(t0, t1, t2, t3, t4, t5, t6, t7, t8, t9) {}
 632
 633
 634   template<class U1, class U2>
 635   tuple(const cons<U1, U2>& p) : inherited(p) {}
 636
 637   template <class U1, class U2>
 638   tuple& operator=(const cons<U1, U2>& k) {
 639     inherited::operator=(k);
 640     return *this;
 641   }
 642
 643   template <class U1, class U2>
 644   tuple& operator=(const std::pair<U1, U2>& k) {
 645     BOOST_STATIC_ASSERT(length<tuple>::value == 2);// check_length = 2
 646     this->head = k.first;
 647     this->tail.head = k.second;
 648     return *this;
 649   }
 650
 651 };
 652
 653 // The empty tuple
 654 template <>
 655 class tuple<null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type, null_type>  :
 656   public null_type
 657 {
 658 public:
 659   typedef null_type inherited;
 660 };
 661
 662
 663 // Swallows any assignment   (by Doug Gregor)
 664 namespace detail {
 665
 666 struct swallow_assign {
 667
 668   template<typename T>
 669   swallow_assign const& operator=(const T&) const {
 670     return *this;
 671   }
 672 };
 673
 674 } // namespace detail
 675
 676 // "ignore" allows tuple positions to be ignored when using "tie".
 677 detail::swallow_assign const ignore = detail::swallow_assign();
 678
 679 // ---------------------------------------------------------------------------
 680 // The call_traits for make_tuple
 681 // Honours the reference_wrapper class.
 682
 683 // Must be instantiated with plain or const plain types (not with references)
 684
 685 // from template<class T> foo(const T& t) : make_tuple_traits<const T>::type
 686 // from template<class T> foo(T& t) : make_tuple_traits<T>::type
 687
 688 // Conversions:
 689 // T -> T,
 690 // references -> compile_time_error
 691 // reference_wrapper<T> -> T&
 692 // const reference_wrapper<T> -> T&
 693 // array -> const ref array
 694
 695
 696 template<class T>
 697 struct make_tuple_traits {
 698   typedef T type;
 699
 700   // commented away, see below  (JJ)
 701   //  typedef typename IF<
 702   //  boost::is_function<T>::value,
 703   //  T&,
 704   //  T>::RET type;
 705
 706 };
 707
 708 // The is_function test was there originally for plain function types,
 709 // which can't be stored as such (we must either store them as references or
 710 // pointers). Such a type could be formed if make_tuple was called with a
 711 // reference to a function.
 712 // But this would mean that a const qualified function type was formed in
 713 // the make_tuple function and hence make_tuple can't take a function
 714 // reference as a parameter, and thus T can't be a function type.
 715 // So is_function test was removed.
 716 // (14.8.3. says that type deduction fails if a cv-qualified function type
 717 // is created. (It only applies for the case of explicitly specifying template
 718 // args, though?)) (JJ)
 719
 720 template<class T>
 721 struct make_tuple_traits<T&> {
 722   typedef typename
 723      detail::generate_error<T&>::
 724        do_not_use_with_reference_type error;
 725 };
 726
 727 // Arrays can't be stored as plain types; convert them to references.
 728 // All arrays are converted to const. This is because make_tuple takes its
 729 // parameters as const T& and thus the knowledge of the potential
 730 // non-constness of actual argument is lost.
 731 template<class T, int n>  struct make_tuple_traits <T[n]> {
 732   typedef const T (&type)[n];
 733 };
 734
 735 template<class T, int n>
 736 struct make_tuple_traits<const T[n]> {
 737   typedef const T (&type)[n];
 738 };
 739
 740 template<class T, int n>  struct make_tuple_traits<volatile T[n]> {
 741   typedef const volatile T (&type)[n];
 742 };
 743
 744 template<class T, int n>
 745 struct make_tuple_traits<const volatile T[n]> {
 746   typedef const volatile T (&type)[n];
 747 };
 748
 749 template<class T>
 750 struct make_tuple_traits<reference_wrapper<T> >{
 751   typedef T& type;
 752 };
 753
 754 template<class T>
 755 struct make_tuple_traits<const reference_wrapper<T> >{
 756   typedef T& type;
 757 };
 758
 759
 760
 761
 762 namespace detail {
 763
 764 // a helper traits to make the make_tuple functions shorter (Vesa Karvonen's
 765 // suggestion)
 766 template <
 767   class T0 = null_type, class T1 = null_type, class T2 = null_type,
 768   class T3 = null_type, class T4 = null_type, class T5 = null_type,
 769   class T6 = null_type, class T7 = null_type, class T8 = null_type,
 770   class T9 = null_type
 771 >
 772 struct make_tuple_mapper {
 773   typedef
 774     tuple<typename make_tuple_traits<T0>::type,
 775           typename make_tuple_traits<T1>::type,
 776           typename make_tuple_traits<T2>::type,
 777           typename make_tuple_traits<T3>::type,
 778           typename make_tuple_traits<T4>::type,
 779           typename make_tuple_traits<T5>::type,
 780           typename make_tuple_traits<T6>::type,
 781           typename make_tuple_traits<T7>::type,
 782           typename make_tuple_traits<T8>::type,
 783           typename make_tuple_traits<T9>::type> type;
 784 };
 785
 786 } // end detail
 787
 788 // -make_tuple function templates -----------------------------------
 789 inline tuple<> make_tuple() {
 790   return tuple<>();
 791 }
 792
 793 template<class T0>
 794 inline typename detail::make_tuple_mapper<T0>::type
 795 make_tuple(const T0& t0) {
 796   typedef typename detail::make_tuple_mapper<T0>::type t;
 797   return t(t0);
 798 }
 799
 800 template<class T0, class T1>
 801 inline typename detail::make_tuple_mapper<T0, T1>::type
 802 make_tuple(const T0& t0, const T1& t1) {
 803   typedef typename detail::make_tuple_mapper<T0, T1>::type t;
 804   return t(t0, t1);
 805 }
 806
 807 template<class T0, class T1, class T2>
 808 inline typename detail::make_tuple_mapper<T0, T1, T2>::type
 809 make_tuple(const T0& t0, const T1& t1, const T2& t2) {
 810   typedef typename detail::make_tuple_mapper<T0, T1, T2>::type t;
 811   return t(t0, t1, t2);
 812 }
 813
 814 template<class T0, class T1, class T2, class T3>
 815 inline typename detail::make_tuple_mapper<T0, T1, T2, T3>::type
 816 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3) {
 817   typedef typename detail::make_tuple_mapper<T0, T1, T2, T3>::type t;
 818   return t(t0, t1, t2, t3);
 819 }
 820
 821 template<class T0, class T1, class T2, class T3, class T4>
 822 inline typename detail::make_tuple_mapper<T0, T1, T2, T3, T4>::type
 823 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 824                   const T4& t4) {
 825   typedef typename detail::make_tuple_mapper<T0, T1, T2, T3, T4>::type t;
 826   return t(t0, t1, t2, t3, t4);
 827 }
 828
 829 template<class T0, class T1, class T2, class T3, class T4, class T5>
 830 inline typename detail::make_tuple_mapper<T0, T1, T2, T3, T4, T5>::type
 831 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 832                   const T4& t4, const T5& t5) {
 833   typedef typename detail::make_tuple_mapper<T0, T1, T2, T3, T4, T5>::type t;
 834   return t(t0, t1, t2, t3, t4, t5);
 835 }
 836
 837 template<class T0, class T1, class T2, class T3, class T4, class T5, class T6>
 838 inline typename detail::make_tuple_mapper<T0, T1, T2, T3, T4, T5, T6>::type
 839 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 840                   const T4& t4, const T5& t5, const T6& t6) {
 841   typedef typename detail::make_tuple_mapper
 842            <T0, T1, T2, T3, T4, T5, T6>::type t;
 843   return t(t0, t1, t2, t3, t4, t5, t6);
 844 }
 845
 846 template<class T0, class T1, class T2, class T3, class T4, class T5, class T6,
 847          class T7>
 848 inline typename detail::make_tuple_mapper<T0, T1, T2, T3, T4, T5, T6, T7>::type
 849 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 850                   const T4& t4, const T5& t5, const T6& t6, const T7& t7) {
 851   typedef typename detail::make_tuple_mapper
 852            <T0, T1, T2, T3, T4, T5, T6, T7>::type t;
 853   return t(t0, t1, t2, t3, t4, t5, t6, t7);
 854 }
 855
 856 template<class T0, class T1, class T2, class T3, class T4, class T5, class T6,
 857          class T7, class T8>
 858 inline typename detail::make_tuple_mapper
 859   <T0, T1, T2, T3, T4, T5, T6, T7, T8>::type
 860 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 861                   const T4& t4, const T5& t5, const T6& t6, const T7& t7,
 862                   const T8& t8) {
 863   typedef typename detail::make_tuple_mapper
 864            <T0, T1, T2, T3, T4, T5, T6, T7, T8>::type t;
 865   return t(t0, t1, t2, t3, t4, t5, t6, t7, t8);
 866 }
 867
 868 template<class T0, class T1, class T2, class T3, class T4, class T5, class T6,
 869          class T7, class T8, class T9>
 870 inline typename detail::make_tuple_mapper
 871   <T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::type
 872 make_tuple(const T0& t0, const T1& t1, const T2& t2, const T3& t3,
 873                   const T4& t4, const T5& t5, const T6& t6, const T7& t7,
 874                   const T8& t8, const T9& t9) {
 875   typedef typename detail::make_tuple_mapper
 876            <T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::type t;
 877   return t(t0, t1, t2, t3, t4, t5, t6, t7, t8, t9);
 878 }
 879
 880
 881
 882 // Tie function templates -------------------------------------------------
 883 template<class T1>
 884 inline tuple<T1&> tie(T1& t1) {
 885   return tuple<T1&> (t1);
 886 }
 887
 888 template<class T1, class T2>
 889 inline tuple<T1&, T2&> tie(T1& t1, T2& t2) {
 890   return tuple<T1&, T2&> (t1, t2);
 891 }
 892
 893 template<class T1, class T2, class T3>
 894 inline tuple<T1&, T2&, T3&> tie(T1& t1, T2& t2, T3& t3) {
 895   return tuple<T1&, T2&, T3&> (t1, t2, t3);
 896 }
 897
 898 template<class T1, class T2, class T3, class T4>
 899 inline tuple<T1&, T2&, T3&, T4&> tie(T1& t1, T2& t2, T3& t3, T4& t4) {
 900   return tuple<T1&, T2&, T3&, T4&> (t1, t2, t3, t4);
 901 }
 902
 903 template<class T1, class T2, class T3, class T4, class T5>
 904 inline tuple<T1&, T2&, T3&, T4&, T5&>
 905 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5) {
 906   return tuple<T1&, T2&, T3&, T4&, T5&> (t1, t2, t3, t4, t5);
 907 }
 908
 909 template<class T1, class T2, class T3, class T4, class T5, class T6>
 910 inline tuple<T1&, T2&, T3&, T4&, T5&, T6&>
 911 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5, T6& t6) {
 912   return tuple<T1&, T2&, T3&, T4&, T5&, T6&> (t1, t2, t3, t4, t5, t6);
 913 }
 914
 915 template<class T1, class T2, class T3, class T4, class T5, class T6, class T7>
 916 inline tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&>
 917 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5, T6& t6, T7& t7) {
 918   return tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&> (t1, t2, t3, t4, t5, t6, t7);
 919 }
 920
 921 template<class T1, class T2, class T3, class T4, class T5, class T6, class T7,
 922          class T8>
 923 inline tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&>
 924 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5, T6& t6, T7& t7, T8& t8) {
 925   return tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&>
 926            (t1, t2, t3, t4, t5, t6, t7, t8);
 927 }
 928
 929 template<class T1, class T2, class T3, class T4, class T5, class T6, class T7,
 930          class T8, class T9>
 931 inline tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&, T9&>
 932 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5, T6& t6, T7& t7, T8& t8,
 933            T9& t9) {
 934   return tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&, T9&>
 935             (t1, t2, t3, t4, t5, t6, t7, t8, t9);
 936 }
 937
 938 template<class T1, class T2, class T3, class T4, class T5, class T6, class T7,
 939          class T8, class T9, class T10>
 940 inline tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&, T9&, T10&>
 941 tie(T1& t1, T2& t2, T3& t3, T4& t4, T5& t5, T6& t6, T7& t7, T8& t8,
 942            T9& t9, T10& t10) {
 943   return tuple<T1&, T2&, T3&, T4&, T5&, T6&, T7&, T8&, T9&, T10&>
 944            (t1, t2, t3, t4, t5, t6, t7, t8, t9, t10);
 945 }
 946
 947 } // end of namespace tuples
 948 } // end of namespace boost
 949
 950
 951 #endif // BOOST_TUPLE_BASIC_HPP
 952
 953