example-bind.cpp revision 8e8fb3be5bd78f0564444eca02b404566a5f3b5d
1// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s 2// expected-no-diagnostics 3 4// Example bind implementation from the variadic templates proposal, 5// ISO C++ committee document number N2080. 6 7// Helper type traits 8template<typename T> 9struct add_reference { 10 typedef T &type; 11}; 12 13template<typename T> 14struct add_reference<T&> { 15 typedef T &type; 16}; 17 18template<typename T> 19struct add_const_reference { 20 typedef T const &type; 21}; 22 23template<typename T> 24struct add_const_reference<T&> { 25 typedef T &type; 26}; 27 28template<typename T, typename U> 29struct is_same { 30 static const bool value = false; 31}; 32 33template<typename T> 34struct is_same<T, T> { 35 static const bool value = true; 36}; 37 38template<typename T> 39class reference_wrapper { 40 T *ptr; 41 42public: 43 reference_wrapper(T& t) : ptr(&t) { } 44 operator T&() const { return *ptr; } 45}; 46 47template<typename T> reference_wrapper<T> ref(T& t) { 48 return reference_wrapper<T>(t); 49} 50template<typename T> reference_wrapper<const T> cref(const T& t) { 51 return reference_wrapper<const T>(t); 52} 53 54template<typename... Values> class tuple; 55 56// Basis case: zero-length tuple 57template<> class tuple<> { }; 58 59template<typename Head, typename... Tail> 60class tuple<Head, Tail...> : private tuple<Tail...> { 61 typedef tuple<Tail...> inherited; 62 63public: 64 tuple() { } 65 // implicit copy-constructor is okay 66 67 // Construct tuple from separate arguments. 68 tuple(typename add_const_reference<Head>::type v, 69 typename add_const_reference<Tail>::type... vtail) 70 : m_head(v), inherited(vtail...) { } 71 72 // Construct tuple from another tuple. 73 template<typename... VValues> tuple(const tuple<VValues...>& other) 74 : m_head(other.head()), inherited(other.tail()) { } 75 76 template<typename... VValues> tuple& 77 operator=(const tuple<VValues...>& other) { 78 m_head = other.head(); 79 tail() = other.tail(); 80 return *this; 81 } 82 83 typename add_reference<Head>::type head() { return m_head; } 84 typename add_reference<const Head>::type head() const { return m_head; } 85 inherited& tail() { return *this; } 86 const inherited& tail() const { return *this; } 87 88protected: 89 Head m_head; 90}; 91 92// Creation functions 93template<typename T> 94struct make_tuple_result { 95 typedef T type; 96}; 97 98template<typename T> 99struct make_tuple_result<reference_wrapper<T> > { 100 typedef T& type; 101}; 102 103template<typename... Values> 104tuple<typename make_tuple_result<Values>::type...> 105make_tuple(const Values&... values) { 106 return tuple<typename make_tuple_result<Values>::type...>(values...); 107} 108 109template<typename... Values> 110tuple<Values&...> tie(Values&... values) { 111 return tuple<Values&...>(values...); 112} 113 114// Helper classes 115template<typename Tuple> struct tuple_size; 116 117template<typename... Values> struct tuple_size<tuple<Values...> > { 118 static const int value = sizeof...(Values); 119}; 120 121template<int I, typename Tuple> struct tuple_element; 122 123template<int I, typename Head, typename... Tail> 124struct tuple_element<I, tuple<Head, Tail...> > { 125 typedef typename tuple_element<I-1, tuple<Tail...> >::type type; 126}; 127 128template<typename Head, typename... Tail> 129struct tuple_element<0, tuple<Head, Tail...> > { 130 typedef Head type; 131}; 132 133// Element access 134template<int I, typename Tuple> class get_impl; 135template<int I, typename Head, typename... Values> 136class get_impl<I, tuple<Head, Values...> > { 137 typedef typename tuple_element<I-1, tuple<Values...> >::type Element; 138 typedef typename add_reference<Element>::type RJ; 139 typedef typename add_const_reference<Element>::type PJ; 140 typedef get_impl<I-1, tuple<Values...> > Next; 141public: 142 static RJ get(tuple<Head, Values...>& t) { return Next::get(t.tail()); } 143 static PJ get(const tuple<Head, Values...>& t) { return Next::get(t.tail()); } 144}; 145 146template<typename Head, typename... Values> 147class get_impl<0, tuple<Head, Values...> > { 148 typedef typename add_reference<Head>::type RJ; 149 typedef typename add_const_reference<Head>::type PJ; 150public: 151 static RJ get(tuple<Head, Values...>& t) { return t.head(); } 152 static PJ get(const tuple<Head, Values...>& t) { return t.head(); } 153}; 154 155template<int I, typename... Values> typename add_reference< 156typename tuple_element<I, tuple<Values...> >::type >::type 157get(tuple<Values...>& t) { 158 return get_impl<I, tuple<Values...> >::get(t); 159} 160 161template<int I, typename... Values> typename add_const_reference< 162typename tuple_element<I, tuple<Values...> >::type >::type 163get(const tuple<Values...>& t) { 164 return get_impl<I, tuple<Values...> >::get(t); 165} 166 167// Relational operators 168inline bool operator==(const tuple<>&, const tuple<>&) { return true; } 169 170template<typename T, typename... TTail, typename U, typename... UTail> 171bool operator==(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u) { 172 return t.head() == u.head() && t.tail() == u.tail(); 173} 174 175template<typename... TValues, typename... UValues> 176bool operator!=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 177 return !(t == u); 178} 179 180inline bool operator<(const tuple<>&, const tuple<>&) { return false; } 181 182template<typename T, typename... TTail, typename U, typename... UTail> 183bool operator<(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u) { 184 return (t.head() < u.head() || (!(t.head() < u.head()) && t.tail() < u.tail())); 185} 186 187template<typename... TValues, typename... UValues> 188bool operator>(const tuple<TValues...>& t, const tuple<UValues...>& u) { 189 return u < t; 190} 191 192template<typename... TValues, typename... UValues> 193bool operator<=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 194 return !(u < t); 195} 196 197template<typename... TValues, typename... UValues> 198bool operator>=(const tuple<TValues...>& t, const tuple<UValues...>& u) { 199 return !(t < u); 200} 201 202// make_indices helper 203template<int...> struct int_tuple {}; 204// make_indexes impl is a helper for make_indexes 205template<int I, typename IntTuple, typename... Types> struct make_indexes_impl; 206 207template<int I, int... Indexes, typename T, typename... Types> 208struct make_indexes_impl<I, int_tuple<Indexes...>, T, Types...> { 209 typedef typename make_indexes_impl<I+1, int_tuple<Indexes..., I>, Types...>::type type; 210}; 211 212template<int I, int... Indexes> 213struct make_indexes_impl<I, int_tuple<Indexes...> > { 214 typedef int_tuple<Indexes...> type; 215}; 216 217template<typename... Types> 218struct make_indexes : make_indexes_impl<0, int_tuple<>, Types...> { 219}; 220 221// Bind 222template<typename T> struct is_bind_expression { 223 static const bool value = false; 224}; 225 226template<typename T> struct is_placeholder { 227 static const int value = 0; 228}; 229 230 231template<typename F, typename... BoundArgs> class bound_functor { 232 typedef typename make_indexes<BoundArgs...>::type indexes; 233public: 234 typedef typename F::result_type result_type; 235 explicit bound_functor(const F& f, const BoundArgs&... bound_args) 236 : f(f), bound_args(bound_args...) { } template<typename... Args> 237 typename F::result_type operator()(Args&... args); 238private: F f; 239 tuple<BoundArgs...> bound_args; 240}; 241 242template<typename F, typename... BoundArgs> 243inline bound_functor<F, BoundArgs...> bind(const F& f, const BoundArgs&... bound_args) { 244 return bound_functor<F, BoundArgs...>(f, bound_args...); 245} 246 247template<typename F, typename ...BoundArgs> 248struct is_bind_expression<bound_functor<F, BoundArgs...> > { 249 static const bool value = true; 250}; 251 252// enable_if helper 253template<bool Cond, typename T = void> 254struct enable_if; 255 256template<typename T> 257struct enable_if<true, T> { 258 typedef T type; 259}; 260 261template<typename T> 262struct enable_if<false, T> { }; 263 264// safe_tuple_element helper 265template<int I, typename Tuple, typename = void> 266struct safe_tuple_element { }; 267 268template<int I, typename... Values> 269struct safe_tuple_element<I, tuple<Values...>, 270 typename enable_if<(I >= 0 && I < tuple_size<tuple<Values...> >::value)>::type> { 271 typedef typename tuple_element<I, tuple<Values...> >::type type; 272}; 273 274// mu 275template<typename Bound, typename... Args> 276inline typename safe_tuple_element<is_placeholder<Bound>::value -1, 277 tuple<Args...> >::type 278mu(Bound& bound_arg, const tuple<Args&...>& args) { 279 return get<is_placeholder<Bound>::value-1>(args); 280} 281 282template<typename T, typename... Args> 283inline T& mu(reference_wrapper<T>& bound_arg, const tuple<Args&...>&) { 284 return bound_arg.get(); 285} 286 287template<typename F, int... Indexes, typename... Args> 288inline typename F::result_type 289unwrap_and_forward(F& f, int_tuple<Indexes...>, const tuple<Args&...>& args) { 290 return f(get<Indexes>(args)...); 291} 292 293template<typename Bound, typename... Args> 294inline typename enable_if<is_bind_expression<Bound>::value, 295 typename Bound::result_type>::type 296mu(Bound& bound_arg, const tuple<Args&...>& args) { 297 typedef typename make_indexes<Args...>::type Indexes; 298 return unwrap_and_forward(bound_arg, Indexes(), args); 299} 300 301template<typename T> 302struct is_reference_wrapper { 303 static const bool value = false; 304}; 305 306template<typename T> 307struct is_reference_wrapper<reference_wrapper<T>> { 308 static const bool value = true; 309}; 310 311template<typename Bound, typename... Args> 312inline typename enable_if<(!is_bind_expression<Bound>::value 313 && !is_placeholder<Bound>::value 314 && !is_reference_wrapper<Bound>::value), 315 Bound&>::type 316mu(Bound& bound_arg, const tuple<Args&...>&) { 317 return bound_arg; 318} 319 320template<typename F, typename... BoundArgs, int... Indexes, typename... Args> 321typename F::result_type apply_functor(F& f, tuple<BoundArgs...>& bound_args, 322 int_tuple<Indexes...>, 323 const tuple<Args&...>& args) { 324 return f(mu(get<Indexes>(bound_args), args)...); 325} 326 327template<typename F, typename... BoundArgs> 328template<typename... Args> 329typename F::result_type bound_functor<F, BoundArgs...>::operator()(Args&... args) { 330 return apply_functor(f, bound_args, indexes(), tie(args...)); 331} 332 333template<int N> struct placeholder { }; 334template<int N> 335struct is_placeholder<placeholder<N>> { 336 static const int value = N; 337}; 338 339template<typename T> 340struct plus { 341 typedef T result_type; 342 343 T operator()(T x, T y) { return x + y; } 344}; 345 346placeholder<1> _1; 347 348// Test bind 349void test_bind() { 350 int x = 17; 351 int y = 25; 352 bind(plus<int>(), x, _1)(y); 353} 354