dune-common  2.8.0
hybridutilities.hh
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1 // -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 // vi: set et ts=4 sw=2 sts=2:
3 #ifndef DUNE_COMMON_HYBRIDUTILITIES_HH
4 #define DUNE_COMMON_HYBRIDUTILITIES_HH
5 
6 #include <tuple>
7 #include <utility>
8 
11 #include <dune/common/fvector.hh>
12 #include <dune/common/indices.hh>
15 
16 
17 
18 namespace Dune {
19 namespace Hybrid {
20 
21 namespace Impl {
22 
23  // Try if tuple_size is implemented for class
24  template<class T, int i>
25  constexpr auto size(const Dune::FieldVector<T, i>&, const PriorityTag<5>&)
26  -> decltype(std::integral_constant<std::size_t,i>())
27  {
28  return {};
29  }
30 
31  // Try if tuple_size is implemented for class
32  template<class T>
33  constexpr auto size(const T&, const PriorityTag<3>&)
34  -> decltype(std::integral_constant<std::size_t,std::tuple_size<T>::value>())
35  {
36  return {};
37  }
38 
39  // Try if there's a static constexpr size()
40  template<class T>
41  constexpr auto size(const T&, const PriorityTag<1>&)
42  -> decltype(std::integral_constant<std::size_t,T::size()>())
43  {
44  return {};
45  }
46 
47  // As a last resort try if there's a static constexpr size()
48  template<class T>
49  constexpr auto size(const T& t, const PriorityTag<0>&)
50  {
51  return t.size();
52  }
53 
54 } // namespace Impl
55 
56 
57 
79 template<class T>
80 constexpr auto size(const T& t)
81 {
82  return Impl::size(t, PriorityTag<42>());
83 }
84 
85 
86 
87 namespace Impl {
88 
89  template<class Container, class Index,
90  std::enable_if_t<IsTuple<std::decay_t<Container>>::value, int> = 0>
91  constexpr decltype(auto) elementAt(Container&& c, Index&&, PriorityTag<2>)
92  {
93  return std::get<std::decay_t<Index>::value>(c);
94  }
95 
96  template<class T, T... t, class Index>
97  constexpr decltype(auto) elementAt(std::integer_sequence<T, t...> c, Index, PriorityTag<1>)
98  {
99  return Dune::integerSequenceEntry(c, std::integral_constant<std::size_t, Index::value>());
100  }
101 
102  template<class Container, class Index>
103  constexpr decltype(auto) elementAt(Container&& c, Index&& i, PriorityTag<0>)
104  {
105  return c[i];
106  }
107 
108 } // namespace Impl
109 
110 
111 
132 template<class Container, class Index>
133 constexpr decltype(auto) elementAt(Container&& c, Index&& i)
134 {
135  return Impl::elementAt(std::forward<Container>(c), std::forward<Index>(i), PriorityTag<42>());
136 }
137 
138 
139 
140 namespace Impl {
141 
142  template<class Begin, class End,
143  std::enable_if_t<IsIntegralConstant<Begin>::value and IsIntegralConstant<End>::value, int> = 0>
144  constexpr auto integralRange(const Begin& /*begin*/, const End& /*end*/, const PriorityTag<1>&)
145  {
146  static_assert(Begin::value <= End::value, "You cannot create an integralRange where end<begin");
148  }
149 
150  // This should be constexpr but gcc-4.9 does not support
151  // the relaxed constexpr requirements. Hence for being
152  // constexpr the function body can only contain a return
153  // statement and no assertion before this.
154  template<class Begin, class End>
155  constexpr auto integralRange(const Begin& begin, const End& end, const PriorityTag<0>&)
156  {
157  return DUNE_ASSERT_AND_RETURN(begin<=end, Dune::IntegralRange<End>(begin, end));
158  }
159 
160 } // namespace Impl
161 
162 
163 
181 template<class Begin, class End>
182 constexpr auto integralRange(const Begin& begin, const End& end)
183 {
184  return Impl::integralRange(begin, end, PriorityTag<42>());
185 }
186 
200 template<class End>
201 constexpr auto integralRange(const End& end)
202 {
204 }
205 
206 
207 
208 namespace Impl {
209 
210  template<class T>
211  constexpr void evaluateFoldExpression(std::initializer_list<T>&&)
212  {}
213 
214  template<class Range, class F, class Index, Index... i>
215  constexpr void forEachIndex(Range&& range, F&& f, std::integer_sequence<Index, i...>)
216  {
217  evaluateFoldExpression<int>({(f(Hybrid::elementAt(range, std::integral_constant<Index,i>())), 0)...});
218  }
219 
220  template<class F, class Index, Index... i>
221  constexpr void forEach(std::integer_sequence<Index, i...> /*range*/, F&& f, PriorityTag<2>)
222  {
223  evaluateFoldExpression<int>({(f(std::integral_constant<Index,i>()), 0)...});
224  }
225 
226 
227  template<class Range, class F,
228  std::enable_if_t<IsIntegralConstant<decltype(Hybrid::size(std::declval<Range>()))>::value, int> = 0>
229  constexpr void forEach(Range&& range, F&& f, PriorityTag<1>)
230  {
231  auto size = Hybrid::size(range);
232  auto indices = std::make_index_sequence<size>();
233  (forEachIndex)(std::forward<Range>(range), std::forward<F>(f), indices);
234  }
235 
236  template<class Range, class F>
237  constexpr void forEach(Range&& range, F&& f, PriorityTag<0>)
238  {
239  for(auto&& e : range)
240  f(e);
241  }
242 
243 } // namespace Impl
244 
245 
246 
265 template<class Range, class F>
266 constexpr void forEach(Range&& range, F&& f)
267 {
268  Impl::forEach(std::forward<Range>(range), std::forward<F>(f), PriorityTag<42>());
269 }
270 
271 
272 
288 template<class Range, class T, class F>
289 constexpr T accumulate(Range&& range, T value, F&& f)
290 {
291  forEach(std::forward<Range>(range), [&](auto&& entry) {
292  value = f(value, entry);
293  });
294  return value;
295 }
296 
297 
298 
299 namespace Impl {
300 
301  struct Id {
302  template<class T>
303  constexpr T operator()(T&& x) const {
304  return std::forward<T>(x);
305  }
306  };
307 
308  template<class IfFunc, class ElseFunc>
309  constexpr decltype(auto) ifElse(std::true_type, IfFunc&& ifFunc, ElseFunc&& /*elseFunc*/)
310  {
311  return ifFunc(Id{});
312  }
313 
314  template<class IfFunc, class ElseFunc>
315  constexpr decltype(auto) ifElse(std::false_type, IfFunc&& /*ifFunc*/, ElseFunc&& elseFunc)
316  {
317  return elseFunc(Id{});
318  }
319 
320  template<class IfFunc, class ElseFunc>
321  decltype(auto) ifElse(const bool& condition, IfFunc&& ifFunc, ElseFunc&& elseFunc)
322  {
323  if (condition)
324  return ifFunc(Id{});
325  else
326  return elseFunc(Id{});
327  }
328 
329 } // namespace Impl
330 
331 
332 
353 template<class Condition, class IfFunc, class ElseFunc>
354 decltype(auto) ifElse(const Condition& condition, IfFunc&& ifFunc, ElseFunc&& elseFunc)
355 {
356  return Impl::ifElse(condition, std::forward<IfFunc>(ifFunc), std::forward<ElseFunc>(elseFunc));
357 }
358 
366 template<class Condition, class IfFunc>
367 void ifElse(const Condition& condition, IfFunc&& ifFunc)
368 {
369  ifElse(condition, std::forward<IfFunc>(ifFunc), [](auto&&) {});
370 }
371 
372 
373 
374 namespace Impl {
375 
376  template<class T1, class T2>
377  constexpr auto equals(const T1& /*t1*/, const T2& /*t2*/, PriorityTag<1>) -> decltype(T1::value, T2::value, std::integral_constant<bool,T1::value == T2::value>())
378  { return {}; }
379 
380  template<class T1, class T2>
381  constexpr auto equals(const T1& t1, const T2& t2, PriorityTag<0>)
382  {
383  return t1==t2;
384  }
385 
386 } // namespace Impl
387 
388 
389 
399 template<class T1, class T2>
400 constexpr auto equals(T1&& t1, T2&& t2)
401 {
402  return Impl::equals(std::forward<T1>(t1), std::forward<T2>(t2), PriorityTag<1>());
403 }
404 
405 
406 
407 namespace Impl {
408 
409  template<class Result, class T, class Value, class Branches, class ElseBranch>
410  constexpr Result switchCases(std::integer_sequence<T>, const Value& /*value*/, Branches&& /*branches*/, ElseBranch&& elseBranch)
411  {
412  return elseBranch();
413  }
414 
415  template<class Result, class T, T t0, T... tt, class Value, class Branches, class ElseBranch>
416  constexpr Result switchCases(std::integer_sequence<T, t0, tt...>, const Value& value, Branches&& branches, ElseBranch&& elseBranch)
417  {
418  return ifElse(
419  Hybrid::equals(std::integral_constant<T, t0>(), value),
420  [&](auto id) -> decltype(auto) {
421  return id(branches)(std::integral_constant<T, t0>());
422  }, [&](auto id) -> decltype(auto) {
423  return Impl::switchCases<Result>(id(std::integer_sequence<T, tt...>()), value, branches, elseBranch);
424  });
425  }
426 
427 } // namespace Impl
428 
429 
430 
458 template<class Cases, class Value, class Branches, class ElseBranch>
459 constexpr decltype(auto) switchCases(const Cases& cases, const Value& value, Branches&& branches, ElseBranch&& elseBranch)
460 {
461  return Impl::switchCases<decltype(elseBranch())>(cases, value, std::forward<Branches>(branches), std::forward<ElseBranch>(elseBranch));
462 }
463 
484 template<class Cases, class Value, class Branches>
485 constexpr void switchCases(const Cases& cases, const Value& value, Branches&& branches)
486 {
487  Impl::switchCases<void>(cases, value, std::forward<Branches>(branches), []() {});
488 }
489 
490 
491 } // namespace Hybrid
492 } // namespace Dune
493 
494 
495 #endif // #ifndef DUNE_COMMON_HYBRIDUTILITIES_HH
Implements a vector constructed from a given type representing a field and a compile-time given size.
Utilities for reduction like operations on ranges.
Traits for type conversions and type information.
Utilities for type computations, constraining overloads, ...
constexpr index_constant< 0 > _0
Compile time index with value 0.
Definition: indices.hh:51
static StaticIntegralRange< T, to, from > range(std::integral_constant< T, from >, std::integral_constant< T, to >) noexcept
Definition: rangeutilities.hh:298
void ifElse(const Condition &condition, IfFunc &&ifFunc)
A conditional expression.
Definition: hybridutilities.hh:367
constexpr auto size(const T &t)
Size query.
Definition: hybridutilities.hh:80
constexpr auto integralRange(const End &end)
Create an integral range starting from 0.
Definition: hybridutilities.hh:201
constexpr auto equals(T1 &&t1, T2 &&t2)
Equality comparison.
Definition: hybridutilities.hh:400
constexpr void forEach(Range &&range, F &&f)
Range based for loop.
Definition: hybridutilities.hh:266
constexpr decltype(auto) switchCases(const Cases &cases, const Value &value, Branches &&branches, ElseBranch &&elseBranch)
Switch statement.
Definition: hybridutilities.hh:459
decltype(auto) ifElse(const Condition &condition, IfFunc &&ifFunc, ElseFunc &&elseFunc)
A conditional expression.
Definition: hybridutilities.hh:354
constexpr auto integralRange(const Begin &begin, const End &end)
Create an integral range.
Definition: hybridutilities.hh:182
constexpr decltype(auto) elementAt(Container &&c, Index &&i)
Get element at given position from container.
Definition: hybridutilities.hh:133
constexpr T accumulate(Range &&range, T value, F &&f)
Accumulate values.
Definition: hybridutilities.hh:289
constexpr auto integerSequenceEntry(std::integer_sequence< T, t... >, std::integral_constant< std::size_t, index > i)
Get entry of std::integer_sequence.
Definition: typetraits.hh:462
#define DUNE_ASSERT_AND_RETURN(C, X)
Asserts a condition and return on success in constexpr context.
Definition: assertandreturn.hh:20
Dune namespace.
Definition: alignedallocator.hh:11
vector space out of a tensor product of fields.
Definition: fvector.hh:95
dynamic integer range for use in range-based for loops
Definition: rangeutilities.hh:173
static integer range for use in range-based for loops
Definition: rangeutilities.hh:223
Check if T is an std::integral_constant<I, i>
Definition: typetraits.hh:384
Helper class for tagging priorities.
Definition: typeutilities.hh:71
Helper class for tagging priorities.
Definition: typeutilities.hh:85