gcc/testsuite/g++.dg/cpp0x/variadic-tuple.C

   1 // { dg-do run { target c++11 } }
   2 // { dg-additional-options "-fexcess-precision=fast" }
   3 // An implementation of TR1's <tuple> using variadic teplates
   4 // Contributed by Douglas Gregor <doug.gregor@gmail.com>
   5
   6 #include <string>
   7 #include <cassert>
   8 #include <cstring>
   9
  10 // Trivial reference_wrapper
  11 template<typename T>
  12 struct reference_wrapper
  13 {
  14   reference_wrapper(T& x) : ptr(&x) { }
  15
  16   operator T&() const { return *ptr; }
  17
  18   T* ptr;
  19 };
  20
  21 template<typename T> reference_wrapper<T> ref(T& x) { return x; }
  22 template<typename T> reference_wrapper<const T> cref(const T& x) { return x; }
  23
  24 // Simple type-traits we'll need
  25 template<typename T>
  26 struct add_reference
  27 {
  28   typedef T& type;
  29 };
  30
  31 template<typename T>
  32 struct add_reference<T&>
  33 {
  34   typedef T& type;
  35 };
  36
  37 template<typename T, typename U>
  38 struct is_same
  39 {
  40   static const bool value = false;
  41 };
  42
  43 template<typename T>
  44 struct is_same<T, T>
  45 {
  46   static const bool value = true;
  47 };
  48
  49 // For creating the constructor parameters of tuple<>
  50 template<typename T>
  51 struct add_const_reference
  52 {
  53   typedef const T& type;
  54 };
  55
  56 template<typename T>
  57 struct add_const_reference<T&>
  58 {
  59   typedef T& type;
  60 };
  61
  62 // 6.1.3 Class template tuple
  63 template<typename... Values>
  64 class tuple;
  65
  66 template<> class tuple<> { };
  67
  68 template<typename Head, typename... Tail>
  69 class tuple<Head, Tail...>
  70   : private tuple<Tail...>
  71 {
  72   typedef tuple<Tail...> inherited;
  73
  74  public:
  75   tuple() { }
  76
  77   // implicit copy-constructor is okay
  78
  79   tuple(typename add_const_reference<Head>::type v,
  80         typename add_const_reference<Tail>::type... vtail)
  81     : m_head(v), inherited(vtail...) { }
  82
  83   template<typename... VValues>
  84   tuple(const tuple<VValues...>& other)
  85     : m_head(other.head()), inherited(other.tail()) { }
  86
  87   template<typename... VValues>
  88   tuple& operator=(const tuple<VValues...>& other)
  89   {
  90     m_head = other.head();
  91     tail() = other.tail();
  92     return *this;
  93   }
  94
  95   typename add_reference<Head>::type       head()       { return m_head; }
  96   typename add_reference<const Head>::type head() const { return m_head; }
  97   inherited&                               tail()       { return *this; }
  98   const inherited&                         tail() const { return *this; }
  99
 100  protected:
 101   Head m_head;
 102 };
 103
 104 template<typename T>
 105 struct make_tuple_result
 106 {
 107   typedef T type;
 108 };
 109
 110 template<typename T>
 111 struct make_tuple_result<reference_wrapper<T> >
 112 {
 113   typedef T& type;
 114 };
 115
 116 // 6.1.3.2 Tuple creation functions
 117 struct ignore_t {
 118   template<typename T> ignore_t& operator=(const T&) { return *this; }
 119 } ignore;
 120
 121 template<typename... Values>
 122 tuple<typename make_tuple_result<Values>::type...>
 123 make_tuple(const Values&... values)
 124 {
 125   return tuple<typename make_tuple_result<Values>::type...>(values...);
 126 }
 127
 128 template<typename... Values>
 129 tuple<Values&...> tie(Values&... values)
 130 {
 131   return tuple<Values&...>(values...);
 132 }
 133
 134 // 6.1.3.3 Tuple helper classes
 135 template<typename Tuple>
 136 struct tuple_size;
 137
 138 template<>
 139 struct tuple_size<tuple<> >
 140 {
 141   static const std::size_t value = 0;
 142 };
 143
 144 template<typename Head, typename... Tail>
 145 struct tuple_size<tuple<Head, Tail...> >
 146 {
 147   static const std::size_t value = 1 + tuple_size<tuple<Tail...> >::value;
 148 };
 149
 150 template<int I, typename Tuple>
 151 struct tuple_element;
 152
 153 template<int I, typename Head, typename... Tail>
 154 struct tuple_element<I, tuple<Head, Tail...> >
 155 {
 156   typedef typename tuple_element<I-1, tuple<Tail...> >::type type;
 157 };
 158
 159 template<typename Head, typename... Tail>
 160 struct tuple_element<0, tuple<Head, Tail...> >
 161 {
 162   typedef Head type;
 163 };
 164
 165 // 6.1.3.4 Element access
 166 template<int I, typename Tuple>
 167 class get_impl;
 168
 169 template<int I, typename Head, typename... Values>
 170 class get_impl<I, tuple<Head, Values...> >
 171 {
 172   typedef typename tuple_element<I-1, tuple<Values...> >::type Element;
 173   typedef typename add_reference<Element>::type RJ;
 174   typedef typename add_const_reference<Element>::type PJ;
 175   typedef get_impl<I-1, tuple<Values...> > Next;
 176
 177  public:
 178   static RJ get(tuple<Head, Values...>& t)
 179   { return Next::get(t.tail()); }
 180
 181   static PJ get(const tuple<Head, Values...>& t)
 182   { return Next::get(t.tail()); }
 183 };
 184
 185 template<typename Head, typename... Values>
 186 class get_impl<0, tuple<Head, Values...> >
 187 {
 188   typedef typename add_reference<Head>::type RJ;
 189   typedef typename add_const_reference<Head>::type PJ;
 190
 191  public:
 192   static RJ get(tuple<Head, Values...>& t)       { return t.head(); }
 193   static PJ get(const tuple<Head, Values...>& t) { return t.head(); }
 194 };
 195
 196 template<int I, typename... Values>
 197 typename add_reference<
 198            typename tuple_element<I, tuple<Values...> >::type
 199          >::type
 200 get(tuple<Values...>& t)
 201 {
 202   return get_impl<I, tuple<Values...> >::get(t);
 203 }
 204
 205 template<int I, typename... Values>
 206 typename add_const_reference<
 207            typename tuple_element<I, tuple<Values...> >::type
 208          >::type
 209 get(const tuple<Values...>& t)
 210 {
 211   return get_impl<I, tuple<Values...> >::get(t);
 212 }
 213
 214 // 6.1.3.5 Relational operators
 215 inline bool operator==(const tuple<>&, const tuple<>&) { return true; }
 216
 217 template<typename T, typename... TTail, typename U, typename... UTail>
 218 bool operator==(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
 219 {
 220   return t.head() == u.head() && t.tail() == u.tail();
 221 }
 222
 223 template<typename... TValues, typename... UValues>
 224 bool operator!=(const tuple<TValues...>& t, const tuple<UValues...>& u)
 225 {
 226   return !(t == u);
 227 }
 228
 229 inline bool operator<(const tuple<>&, const tuple<>&) { return false; }
 230
 231 template<typename T, typename... TTail, typename U, typename... UTail>
 232 bool operator<(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
 233 {
 234   return (t.head() < u.head() ||
 235           (!(t.head() < u.head()) && t.tail() < u.tail()));
 236 }
 237
 238 template<typename... TValues, typename... UValues>
 239 bool operator>(const tuple<TValues...>& t, const tuple<UValues...>& u)
 240 {
 241   return u < t;
 242 }
 243
 244 template<typename... TValues, typename... UValues>
 245 bool operator<=(const tuple<TValues...>& t, const tuple<UValues...>& u)
 246 {
 247   return !(u < t);
 248 }
 249
 250 template<typename... TValues, typename... UValues>
 251 bool operator>=(const tuple<TValues...>& t, const tuple<UValues...>& u)
 252 {
 253   return !(t < u);
 254 }
 255
 256 int a0[tuple_size<tuple<> >::value == 0? 1 : -1];
 257 int a1[tuple_size<tuple<int, float, double> >::value == 3? 1 : -1];
 258 int a2a[is_same<tuple_element<0, tuple<int, float, double> >::type, int>
 259          ::value? 1 : -1];
 260 int a2b[is_same<tuple_element<1, tuple<int, float, double> >::type, float>
 261          ::value? 1 : -1];
 262 int a2c[is_same<tuple_element<2, tuple<int, float, double> >::type, double>
 263          ::value? 1 : -1];
 264
 265 int main()
 266 {
 267   tuple<> t0;
 268   tuple<int> t1(1);
 269   tuple<int, float> t2(1, 3.14159f);
 270   tuple<int, float, const char*> t3a(1, 3.14159f, "Hello, world!");
 271   tuple<long, double, std::string> t3b(t3a);
 272   t3b = t3a;
 273   //  t3a = t3b; DPG: triggers an error, as it should.
 274
 275   tuple<int, float, std::string> t3c =
 276     ::make_tuple(17, 2.718281828, std::string("Fun"));
 277
 278   int seventeen = 17;
 279   double pi = 3.14159;
 280   tuple<int&, double&> seventeen_pi = make_tuple(ref(seventeen), ref(pi));
 281   tuple<int&, const double&> seventeen_pi2 =
 282     make_tuple(ref(seventeen), cref(pi));
 283   tuple<int&, double&> seventeen_pi_tied = tie(seventeen, pi);
 284   assert(get<0>(t3a) == 1);
 285   assert(get<1>(t3a) == 3.14159f);
 286   assert(std::strcmp(get<2>(t3a), "Hello, world!") == 0);
 287
 288   assert(t3a == t3b);
 289   assert(!(t3a != t3b));
 290   assert(!(t3a < t3b));
 291   assert(!(t3a > t3b));
 292   assert(t3a <= t3b && t3b <= t3a);
 293   assert(t3a >= t3b && t3b >= t3a);
 294 }