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