1 // { dg-do run { target c++11 } }
2 // An implementation of TR1's <tuple> using variadic teplates
3 // Contributed by Douglas Gregor <doug.gregor@gmail.com>
4
5 #include <string>
6 #include <cassert>
7 #include <cstring>
8
9 // Trivial reference_wrapper
10 template<typename T>
11 struct reference_wrapper
12 {
reference_wrapperreference_wrapper13 reference_wrapper(T& x) : ptr(&x) { }
14
15 operator T&() const { return *ptr; }
16
17 T* ptr;
18 };
19
ref(T & x)20 template<typename T> reference_wrapper<T> ref(T& x) { return x; }
cref(const T & x)21 template<typename T> reference_wrapper<const T> cref(const T& x) { return x; }
22
23 // Simple type-traits we'll need
24 template<typename T>
25 struct add_reference
26 {
27 typedef T& type;
28 };
29
30 template<typename T>
31 struct add_reference<T&>
32 {
33 typedef T& type;
34 };
35
36 template<typename T, typename U>
37 struct is_same
38 {
39 static const bool value = false;
40 };
41
42 template<typename T>
43 struct is_same<T, T>
44 {
45 static const bool value = true;
46 };
47
48 // For creating the constructor parameters of tuple<>
49 template<typename T>
50 struct add_const_reference
51 {
52 typedef const T& type;
53 };
54
55 template<typename T>
56 struct add_const_reference<T&>
57 {
58 typedef T& type;
59 };
60
61 // 6.1.3 Class template tuple
62 template<typename... Values>
63 class tuple;
64
65 template<> class tuple<> { };
66
67 template<typename Head, typename... Tail>
68 class tuple<Head, Tail...>
69 : private tuple<Tail...>
70 {
71 typedef tuple<Tail...> inherited;
72
73 public:
74 tuple() { }
75
76 // implicit copy-constructor is okay
77
78 tuple(typename add_const_reference<Head>::type v,
79 typename add_const_reference<Tail>::type... vtail)
80 : m_head(v), inherited(vtail...) { }
81
82 template<typename... VValues>
83 tuple(const tuple<VValues...>& other)
84 : m_head(other.head()), inherited(other.tail()) { }
85
86 template<typename... VValues>
87 tuple& operator=(const tuple<VValues...>& other)
88 {
89 m_head = other.head();
90 tail() = other.tail();
91 return *this;
92 }
93
94 typename add_reference<Head>::type head() { return m_head; }
95 typename add_reference<const Head>::type head() const { return m_head; }
96 inherited& tail() { return *this; }
97 const inherited& tail() const { return *this; }
98
99 protected:
100 Head m_head;
101 };
102
103 template<typename T>
104 struct make_tuple_result
105 {
106 typedef T type;
107 };
108
109 template<typename T>
110 struct make_tuple_result<reference_wrapper<T> >
111 {
112 typedef T& type;
113 };
114
115 // 6.1.3.2 Tuple creation functions
116 struct ignore_t {
117 template<typename T> ignore_t& operator=(const T&) { return *this; }
118 } ignore;
119
120 template<typename... Values>
121 tuple<typename make_tuple_result<Values>::type...>
122 make_tuple(const Values&... values)
123 {
124 return tuple<typename make_tuple_result<Values>::type...>(values...);
125 }
126
127 template<typename... Values>
128 tuple<Values&...> tie(Values&... values)
129 {
130 return tuple<Values&...>(values...);
131 }
132
133 // 6.1.3.3 Tuple helper classes
134 template<typename Tuple>
135 struct tuple_size;
136
137 template<>
138 struct tuple_size<tuple<> >
139 {
140 static const std::size_t value = 0;
141 };
142
143 template<typename Head, typename... Tail>
144 struct tuple_size<tuple<Head, Tail...> >
145 {
146 static const std::size_t value = 1 + tuple_size<tuple<Tail...> >::value;
147 };
148
149 template<int I, typename Tuple>
150 struct tuple_element;
151
152 template<int I, typename Head, typename... Tail>
153 struct tuple_element<I, tuple<Head, Tail...> >
154 {
155 typedef typename tuple_element<I-1, tuple<Tail...> >::type type;
156 };
157
158 template<typename Head, typename... Tail>
159 struct tuple_element<0, tuple<Head, Tail...> >
160 {
161 typedef Head type;
162 };
163
164 // 6.1.3.4 Element access
165 template<int I, typename Tuple>
166 class get_impl;
167
168 template<int I, typename Head, typename... Values>
169 class get_impl<I, tuple<Head, Values...> >
170 {
171 typedef typename tuple_element<I-1, tuple<Values...> >::type Element;
172 typedef typename add_reference<Element>::type RJ;
173 typedef typename add_const_reference<Element>::type PJ;
174 typedef get_impl<I-1, tuple<Values...> > Next;
175
176 public:
177 static RJ get(tuple<Head, Values...>& t)
178 { return Next::get(t.tail()); }
179
180 static PJ get(const tuple<Head, Values...>& t)
181 { return Next::get(t.tail()); }
182 };
183
184 template<typename Head, typename... Values>
185 class get_impl<0, tuple<Head, Values...> >
186 {
187 typedef typename add_reference<Head>::type RJ;
188 typedef typename add_const_reference<Head>::type PJ;
189
190 public:
191 static RJ get(tuple<Head, Values...>& t) { return t.head(); }
192 static PJ get(const tuple<Head, Values...>& t) { return t.head(); }
193 };
194
195 template<int I, typename... Values>
196 typename add_reference<
197 typename tuple_element<I, tuple<Values...> >::type
198 >::type
199 get(tuple<Values...>& t)
200 {
201 return get_impl<I, tuple<Values...> >::get(t);
202 }
203
204 template<int I, typename... Values>
205 typename add_const_reference<
206 typename tuple_element<I, tuple<Values...> >::type
207 >::type
208 get(const tuple<Values...>& t)
209 {
210 return get_impl<I, tuple<Values...> >::get(t);
211 }
212
213 // 6.1.3.5 Relational operators
214 inline bool operator==(const tuple<>&, const tuple<>&) { return true; }
215
216 template<typename T, typename... TTail, typename U, typename... UTail>
217 bool operator==(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
218 {
219 return t.head() == u.head() && t.tail() == u.tail();
220 }
221
222 template<typename... TValues, typename... UValues>
223 bool operator!=(const tuple<TValues...>& t, const tuple<UValues...>& u)
224 {
225 return !(t == u);
226 }
227
228 inline bool operator<(const tuple<>&, const tuple<>&) { return false; }
229
230 template<typename T, typename... TTail, typename U, typename... UTail>
231 bool operator<(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
232 {
233 return (t.head() < u.head() ||
234 (!(t.head() < u.head()) && t.tail() < u.tail()));
235 }
236
237 template<typename... TValues, typename... UValues>
238 bool operator>(const tuple<TValues...>& t, const tuple<UValues...>& u)
239 {
240 return u < t;
241 }
242
243 template<typename... TValues, typename... UValues>
244 bool operator<=(const tuple<TValues...>& t, const tuple<UValues...>& u)
245 {
246 return !(u < t);
247 }
248
249 template<typename... TValues, typename... UValues>
250 bool operator>=(const tuple<TValues...>& t, const tuple<UValues...>& u)
251 {
252 return !(t < u);
253 }
254
255 int a0[tuple_size<tuple<> >::value == 0? 1 : -1];
256 int a1[tuple_size<tuple<int, float, double> >::value == 3? 1 : -1];
257 int a2a[is_same<tuple_element<0, tuple<int, float, double> >::type, int>
258 ::value? 1 : -1];
259 int a2b[is_same<tuple_element<1, tuple<int, float, double> >::type, float>
260 ::value? 1 : -1];
261 int a2c[is_same<tuple_element<2, tuple<int, float, double> >::type, double>
262 ::value? 1 : -1];
263
264 int main()
265 {
266 tuple<> t0;
267 tuple<int> t1(1);
268 tuple<int, float> t2(1, 3.14159f);
269 tuple<int, float, const char*> t3a(1, 3.14159f, "Hello, world!");
270 tuple<long, double, std::string> t3b(t3a);
271 t3b = t3a;
272 // t3a = t3b; DPG: triggers an error, as it should.
273
274 tuple<int, float, std::string> t3c =
275 make_tuple(17, 2.718281828, std::string("Fun"));
276
277 int seventeen = 17;
278 double pi = 3.14159;
279 tuple<int&, double&> seventeen_pi = make_tuple(ref(seventeen), ref(pi));
280 tuple<int&, const double&> seventeen_pi2 =
281 make_tuple(ref(seventeen), cref(pi));
282 tuple<int&, double&> seventeen_pi_tied = tie(seventeen, pi);
283 assert(get<0>(t3a) == 1);
284 assert(get<1>(t3a) == 3.14159f);
285 assert(std::strcmp(get<2>(t3a), "Hello, world!") == 0);
286
287 assert(t3a == t3b);
288 assert(!(t3a != t3b));
289 assert(!(t3a < t3b));
290 assert(!(t3a > t3b));
291 assert(t3a <= t3b && t3b <= t3a);
292 assert(t3a >= t3b && t3b >= t3a);
293 }
294