1 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s 2 3 // Example bind implementation from the variadic templates proposal, 4 // ISO C++ committee document number N2080. 5 6 // Helper type traits 7 template<typename T> 8 struct add_reference { 9 typedef T &type; 10 }; 11 12 template<typename T> 13 struct add_reference<T&> { 14 typedef T &type; 15 }; 16 17 template<typename T> 18 struct add_const_reference { 19 typedef T const &type; 20 }; 21 22 template<typename T> 23 struct add_const_reference<T&> { 24 typedef T &type; 25 }; 26 27 template<typename T, typename U> 28 struct is_same { 29 static const bool value = false; 30 }; 31 32 template<typename T> 33 struct is_same<T, T> { 34 static const bool value = true; 35 }; 36 37 template<typename T> 38 class reference_wrapper { 39 T *ptr; 40 41 public: 42 reference_wrapper(T& t) : ptr(&t) { } 43 operator T&() const { return *ptr; } 44 }; 45 46 template<typename T> reference_wrapper<T> ref(T& t) { 47 return reference_wrapper<T>(t); 48 } 49 template<typename T> reference_wrapper<const T> cref(const T& t) { 50 return reference_wrapper<const T>(t); 51 } 52 53 template<typename... Values> class tuple; 54 55 // Basis case: zero-length tuple 56 template<> class tuple<> { }; 57 58 template<typename Head, typename... Tail> 59 class tuple<Head, Tail...> : private tuple<Tail...> { 60 typedef tuple<Tail...> inherited; 61 62 public: 63 tuple() { } 64 // implicit copy-constructor is okay 65 66 // Construct tuple from separate arguments. 67 tuple(typename add_const_reference<Head>::type v, 68 typename add_const_reference<Tail>::type... vtail) 69 : m_head(v), inherited(vtail...) { } 70 71 // Construct tuple from another tuple. 72 template<typename... VValues> tuple(const tuple<VValues...>& other) 73 : m_head(other.head()), inherited(other.tail()) { } 74 75 template<typename... VValues> tuple& 76 operator=(const tuple<VValues...>& other) { 77 m_head = other.head(); 78 tail() = other.tail(); 79 return *this; 80 } 81 82 typename add_reference<Head>::type head() { return m_head; } 83 typename add_reference<const Head>::type head() const { return m_head; } 84 inherited& tail() { return *this; } 85 const inherited& tail() const { return *this; } 86 87 protected: 88 Head m_head; 89 }; 90 91 // Creation functions 92 template<typename T> 93 struct make_tuple_result { 94 typedef T type; 95 }; 96 97 template<typename T> 98 struct make_tuple_result<reference_wrapper<T> > { 99 typedef T& type; 100 }; 101 102 template<typename... Values> 103 tuple<typename make_tuple_result<Values>::type...> 104 make_tuple(const Values&... values) { 105 return tuple<typename make_tuple_result<Values>::type...>(values...); 106 } 107 108 template<typename... Values> 109 tuple<Values&...> tie(Values&... values) { 110 return tuple<Values&...>(values...); 111 } 112 113 // Helper classes 114 template<typename Tuple> struct tuple_size; 115 116 template<typename... Values> struct tuple_size<tuple<Values...> > { 117 static const int value = sizeof...(Values); 118 }; 119 120 template<int I, typename Tuple> struct tuple_element; 121 122 template<int I, typename Head, typename... Tail> 123 struct tuple_element<I, tuple<Head, Tail...> > { 124 typedef typename tuple_element<I-1, tuple<Tail...> >::type type; 125 }; 126 127 template<typename Head, typename... Tail> 128 struct tuple_element<0, tuple<Head, Tail...> > { 129 typedef Head type; 130 }; 131 132 // Element access 133 template<int I, typename Tuple> class get_impl; 134 template<int I, typename Head, typename... Values> 135 class get_impl<I, tuple<Head, Values...> > { 136 typedef typename tuple_element<I-1, tuple<Values...> >::type Element; 137 typedef typename add_reference<Element>::type RJ; 138 typedef typename add_const_reference<Element>::type PJ; 139 typedef get_impl<I-1, tuple<Values...> > Next; 140 public: 141 static RJ get(tuple<Head, Values...>& t) { return Next::get(t.tail()); } 142 static PJ get(const tuple<Head, Values...>& t) { return Next::get(t.tail()); } 143 }; 144 145 template<typename Head, typename... Values> 146 class get_impl<0, tuple<Head, Values...> > { 147 typedef typename add_reference<Head>::type RJ; 148 typedef typename add_const_reference<Head>::type PJ; 149 public: 150 static RJ get(tuple<Head, Values...>& t) { return t.head(); } 151 static PJ get(const tuple<Head, Values...>& t) { return t.head(); } 152 }; 153 154 template<int I, typename... Values> typename add_reference< 155 typename tuple_element<I, tuple<Values...> >::type >::type 156 get(tuple<Values...>& t) { 157 return get_impl<I, tuple<Values...> >::get(t); 158 } 159 160 template<int I, typename... Values> typename add_const_reference< 161 typename tuple_element<I, tuple<Values...> >::type >::type 162 get(const tuple<Values...>& t) { 163 return get_impl<I, tuple<Values...> >::get(t); 164 } 165 166 // Relational operators 167 inline bool operator==(const tuple<>&, const tuple<>&) { return true; } 168 169 template<typename T, typename... TTail, typename U, typename... UTail> 170 bool operator==(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u) { 171 return t.head() == u.head() && t.tail() == u.tail(); 172 } 173 174 template<typename... TValues, typename... UValues> 175 bool operator!=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 176 return !(t == u); 177 } 178 179 inline bool operator<(const tuple<>&, const tuple<>&) { return false; } 180 181 template<typename T, typename... TTail, typename U, typename... UTail> 182 bool operator<(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u) { 183 return (t.head() < u.head() || (!(t.head() < u.head()) && t.tail() < u.tail())); 184 } 185 186 template<typename... TValues, typename... UValues> 187 bool operator>(const tuple<TValues...>& t, const tuple<UValues...>& u) { 188 return u < t; 189 } 190 191 template<typename... TValues, typename... UValues> 192 bool operator<=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 193 return !(u < t); 194 } 195 196 template<typename... TValues, typename... UValues> 197 bool operator>=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 198 return !(t < u); 199 } 200 201 // make_indices helper 202 template<int...> struct int_tuple {}; 203 // make_indexes impl is a helper for make_indexes 204 template<int I, typename IntTuple, typename... Types> struct make_indexes_impl; 205 206 template<int I, int... Indexes, typename T, typename... Types> 207 struct make_indexes_impl<I, int_tuple<Indexes...>, T, Types...> { 208 typedef typename make_indexes_impl<I+1, int_tuple<Indexes..., I>, Types...>::type type; 209 }; 210 211 template<int I, int... Indexes> 212 struct make_indexes_impl<I, int_tuple<Indexes...> > { 213 typedef int_tuple<Indexes...> type; 214 }; 215 216 template<typename... Types> 217 struct make_indexes : make_indexes_impl<0, int_tuple<>, Types...> { 218 }; 219 220 // Bind 221 template<typename T> struct is_bind_expression { 222 static const bool value = false; 223 }; 224 225 template<typename T> struct is_placeholder { 226 static const int value = 0; 227 }; 228 229 230 template<typename F, typename... BoundArgs> class bound_functor { 231 typedef typename make_indexes<BoundArgs...>::type indexes; 232 public: 233 typedef typename F::result_type result_type; 234 explicit bound_functor(const F& f, const BoundArgs&... bound_args) 235 : f(f), bound_args(bound_args...) { } template<typename... Args> 236 typename F::result_type operator()(Args&... args); 237 private: F f; 238 tuple<BoundArgs...> bound_args; 239 }; 240 241 template<typename F, typename... BoundArgs> 242 inline bound_functor<F, BoundArgs...> bind(const F& f, const BoundArgs&... bound_args) { 243 return bound_functor<F, BoundArgs...>(f, bound_args...); 244 } 245 246 template<typename F, typename ...BoundArgs> 247 struct is_bind_expression<bound_functor<F, BoundArgs...> > { 248 static const bool value = true; 249 }; 250 251 // enable_if helper 252 template<bool Cond, typename T = void> 253 struct enable_if; 254 255 template<typename T> 256 struct enable_if<true, T> { 257 typedef T type; 258 }; 259 260 template<typename T> 261 struct enable_if<false, T> { }; 262 263 // safe_tuple_element helper 264 template<int I, typename Tuple, typename = void> 265 struct safe_tuple_element { }; 266 267 template<int I, typename... Values> 268 struct safe_tuple_element<I, tuple<Values...>, 269 typename enable_if<(I >= 0 && I < tuple_size<tuple<Values...> >::value)>::type> { 270 typedef typename tuple_element<I, tuple<Values...> >::type type; 271 }; 272 273 // mu 274 template<typename Bound, typename... Args> 275 inline typename safe_tuple_element<is_placeholder<Bound>::value -1, 276 tuple<Args...> >::type 277 mu(Bound& bound_arg, const tuple<Args&...>& args) { 278 return get<is_placeholder<Bound>::value-1>(args); 279 } 280 281 template<typename T, typename... Args> 282 inline T& mu(reference_wrapper<T>& bound_arg, const tuple<Args&...>&) { 283 return bound_arg.get(); 284 } 285 286 template<typename F, int... Indexes, typename... Args> 287 inline typename F::result_type 288 unwrap_and_forward(F& f, int_tuple<Indexes...>, const tuple<Args&...>& args) { 289 return f(get<Indexes>(args)...); 290 } 291 292 template<typename Bound, typename... Args> 293 inline typename enable_if<is_bind_expression<Bound>::value, 294 typename Bound::result_type>::type 295 mu(Bound& bound_arg, const tuple<Args&...>& args) { 296 typedef typename make_indexes<Args...>::type Indexes; 297 return unwrap_and_forward(bound_arg, Indexes(), args); 298 } 299 300 template<typename T> 301 struct is_reference_wrapper { 302 static const bool value = false; 303 }; 304 305 template<typename T> 306 struct is_reference_wrapper<reference_wrapper<T>> { 307 static const bool value = true; 308 }; 309 310 template<typename Bound, typename... Args> 311 inline typename enable_if<(!is_bind_expression<Bound>::value 312 && !is_placeholder<Bound>::value 313 && !is_reference_wrapper<Bound>::value), 314 Bound&>::type 315 mu(Bound& bound_arg, const tuple<Args&...>&) { 316 return bound_arg; 317 } 318 319 template<typename F, typename... BoundArgs, int... Indexes, typename... Args> 320 typename F::result_type apply_functor(F& f, tuple<BoundArgs...>& bound_args, 321 int_tuple<Indexes...>, 322 const tuple<Args&...>& args) { 323 return f(mu(get<Indexes>(bound_args), args)...); 324 } 325 326 template<typename F, typename... BoundArgs> 327 template<typename... Args> 328 typename F::result_type bound_functor<F, BoundArgs...>::operator()(Args&... args) { 329 return apply_functor(f, bound_args, indexes(), tie(args...)); 330 } 331 332 template<int N> struct placeholder { }; 333 template<int N> 334 struct is_placeholder<placeholder<N>> { 335 static const int value = N; 336 }; 337 338 template<typename T> 339 struct plus { 340 typedef T result_type; 341 342 T operator()(T x, T y) { return x + y; } 343 }; 344 345 placeholder<1> _1; 346 347 // Test bind 348 void test_bind() { 349 int x = 17; 350 int y = 25; 351 bind(plus<int>(), x, _1)(y); 352 } 353
