Dune Core Modules (2.4.1)

typetraits.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_TYPETRAITS_HH
4#define DUNE_TYPETRAITS_HH
5
6#include <type_traits>
7
9#include <dune/common/std/utility.hh>
10
11namespace Dune
12{
13
27 struct Empty {};
28
39 template <typename T>
41 {
42 private:
43 template <class U>
44 struct PointerTraits {
45 enum { result = false };
46 typedef Empty PointeeType;
47 };
48
49 template <class U>
50 struct PointerTraits<U*> {
51 enum { result = true };
52 typedef U PointeeType;
53 };
54
55 template <class U> struct ReferenceTraits
56 {
57 enum { result = false };
58 typedef U ReferredType;
59 };
60
61 template <class U> struct ReferenceTraits<U&>
62 {
63 enum { result = true };
64 typedef U ReferredType;
65 };
66
67 public:
68 enum { isPointer = PointerTraits<T>::result };
69 typedef typename PointerTraits<T>::PointeeType PointeeType DUNE_DEPRECATED_MSG("Use remove_pointer instead!");
70
71 enum { isReference = ReferenceTraits<T>::result };
72 typedef typename ReferenceTraits<T>::ReferredType ReferredType DUNE_DEPRECATED_MSG("Use remove_reference instead!");
73 };
74
79 template<typename T>
81 {
82 enum {
86 isConst=false
87 };
88
90 typedef T UnqualifiedType;
92 typedef const T ConstType;
94 typedef const volatile T ConstVolatileType;
95 };
96
97 template<typename T>
98 struct ConstantVolatileTraits<const T>
99 {
100 enum {
101 isVolatile=false, isConst=true
102 };
103 typedef T UnqualifiedType;
104 typedef const UnqualifiedType ConstType;
105 typedef const volatile UnqualifiedType ConstVolatileType;
106 };
107
108
109 template<typename T>
110 struct ConstantVolatileTraits<volatile T>
111 {
112 enum {
113 isVolatile=true, isConst=false
114 };
115 typedef T UnqualifiedType;
116 typedef const UnqualifiedType ConstType;
117 typedef const volatile UnqualifiedType ConstVolatileType;
118 };
119
120 template<typename T>
121 struct ConstantVolatileTraits<const volatile T>
122 {
123 enum {
124 isVolatile=true, isConst=true
125 };
126 typedef T UnqualifiedType;
127 typedef const UnqualifiedType ConstType;
128 typedef const volatile UnqualifiedType ConstVolatileType;
129 };
130
132 template<typename T>
134 {
135 enum {
138 };
139 };
140
142 template<typename T>
143 struct IsConst
144 {
145 enum {
148 };
149 };
150
151 template<typename T, bool isVolatile>
152 struct RemoveConstHelper
153 {
154 typedef typename ConstantVolatileTraits<T>::UnqualifiedType Type;
155 };
156
157 template<typename T>
158 struct RemoveConstHelper<T,true>
159 {
160 typedef volatile typename ConstantVolatileTraits<T>::UnqualifiedType Type;
161 };
162
163 using std::remove_const;
164 using std::remove_reference;
165
175 template<class From, class To>
177 {
178 typedef char Small;
179 struct Big {char dummy[2];};
180 static Small test(To);
181 static Big test(...);
182 static typename remove_reference< From >::type &makeFrom ();
183
184 public:
185 enum {
187 exists = sizeof(test(makeFrom())) == sizeof(Small),
191 sameType = false
192 };
193 Conversion(){}
194
195 };
196
197 template <class From>
198 class Conversion<From, void>
199 {
200 public:
201 enum {
202 exists = false,
203 isTwoWay = false,
204 sameType = false
205 };
206 };
207
208 template <class To>
209 class Conversion<void, To>
210 {
211 public:
212 enum {
213 exists = false,
214 isTwoWay = false,
215 sameType = false
216 };
217 };
218
219 template<>
220 class Conversion< int, double >
221 {
222 public:
223 enum {
224 exists = true,
225 isTwoWay = false,
226 sameType = false
227 };
228 };
229
230 template<class T>
231 class Conversion<T,T>{
232 public:
233 enum { exists=true, isTwoWay=true, sameType=true};
234 };
235
245 template <class Base, class Derived>
247 {
248 typedef typename ConstantVolatileTraits< typename remove_reference< Base >::type >::UnqualifiedType RawBase;
249 typedef typename ConstantVolatileTraits< typename remove_reference< Derived >::type >::UnqualifiedType RawDerived;
250 typedef char Small;
251 struct Big {char dummy[2];};
252 static Small test(RawBase*);
253 static Big test(...);
254 static RawDerived* &makePtr ();
255 public:
256 enum {
258 value = sizeof(test(makePtr())) == sizeof(Small)
259 };
260 IsBaseOf(){}
261
262 };
263
270 template<class T1, class T2>
272 {
273 enum {
279 };
280 };
281
282 using std::enable_if;
283
289 template<class T1, class T2, class Type>
291 : public enable_if<IsInteroperable<T1,T2>::value, Type>
292 {};
293
294 // pull in default implementation
295 using std::is_same;
296 using std::conditional;
297 using std::integral_constant;
298 using std::true_type;
299 using std::false_type;
300
301
302 template<typename>
303 struct __is_pointer_helper
304 : public false_type { };
305
306 template<typename T>
307 struct __is_pointer_helper<T*>
308 : public true_type { };
309
311 template<typename T>
313 : public integral_constant<bool, (__is_pointer_helper<T>::value)>
314 { };
315
316 // Helper class for is_lvalue_reference
317 template<typename>
318 struct __is_lvalue_reference_helper
319 : public false_type { };
320
321 template<typename T>
322 struct __is_lvalue_reference_helper<T&>
323 : public true_type { };
324
326 template<typename T>
328 : public integral_constant<bool, (__is_lvalue_reference_helper<T>::value)>
329 { };
330
331 template<typename _Tp>
332 struct __remove_pointer_helper
333 { typedef _Tp type; };
334
335 template<typename _Tp>
336 struct __remove_pointer_helper<_Tp*>
337 { typedef _Tp type; };
338
344 template<typename _Tp>
346 : public __remove_pointer_helper<typename remove_const<_Tp>::type >
347 { };
348
366
382
389 template<typename T>
390 struct AlwaysFalse {
392 static const bool value = false;
393 };
394
402 template<typename T>
403 struct AlwaysTrue {
405 static const bool value = true;
406 };
407
408
409#if defined(DOXYGEN) or HAVE_IS_INDEXABLE_SUPPORT
410
411#ifndef DOXYGEN
412
413 namespace detail {
414
415 template<typename T, typename I, typename = int>
416 struct _is_indexable
417 : public std::false_type
418 {};
419
420 template<typename T, typename I>
421 struct _is_indexable<T,I,typename std::enable_if<(sizeof(Std::declval<T>()[Std::declval<I>()]) > 0),int>::type>
422 : public std::true_type
423 {};
424
425 }
426
427#endif // DOXYGEN
428
431
435 template<typename T, typename I = std::size_t>
437 : public detail::_is_indexable<T,I>
438 {};
439
440
441#else // defined(DOXYGEN) or HAVE_IS_INDEXABLE_SUPPORT
442
443
444 // okay, here follows a mess of compiler bug workarounds...
445 // GCC 4.4 dies if we try to subscript a simple type like int and
446 // both GCC 4.4 and 4.5 don't like using arbitrary types as subscripts
447 // for macros.
448 // So we make sure to only ever attempt the SFINAE for operator[] for
449 // class types, and to make sure the compiler doesn't become overly eager
450 // we have to do some lazy evaluation tricks with nested templates and
451 // stuff.
452 // Let's get rid of GCC 4.4 ASAP!
453
454
455 namespace detail {
456
457 // simple wrapper template to support the lazy evaluation required
458 // in _is_indexable
459 template<typename T>
460 struct _lazy
461 {
462 template<typename U>
463 struct evaluate
464 {
465 typedef T type;
466 };
467 };
468
469 // default version, gets picked if SFINAE fails
470 template<typename T, typename = int>
471 struct _is_indexable
472 : public std::false_type
473 {};
474
475 // version for types supporting the subscript operation
476 template<typename T>
477 struct _is_indexable<T,decltype(Std::declval<T>()[0],0)>
478 : public std::true_type
479 {};
480
481 // helper struct for delaying the evaluation until we are sure
482 // that T is a class (i.e. until we are outside std::conditional
483 // below)
484 struct _check_for_index_operator
485 {
486
487 template<typename T>
488 struct evaluate
489 : public _is_indexable<T>
490 {};
491
492 };
493
494 }
495
496 // The rationale here is as follows:
497 // 1) If we have an array, we assume we can index into it. That isn't
498 // true if I isn't an integral type, but that's why we have the static assertion
499 // in the body - we could of course try and check whether I is integral, but I
500 // can't be arsed and want to provide a motivation to switch to a newer compiler...
501 // 2) If we have a class, we use SFINAE to check for operator[]
502 // 3) Otherwise, we assume that T does not support indexing
503 //
504 // In order to make sure that the compiler doesn't accidentally try the SFINAE evaluation
505 // on an array or a scalar, we have to resort to lazy evaluation.
506 template<typename T, typename I = std::size_t>
507 struct is_indexable
508 : public std::conditional<
509 std::is_array<T>::value,
510 detail::_lazy<std::true_type>,
511 typename std::conditional<
512 std::is_class<T>::value,
513 detail::_check_for_index_operator,
514 detail::_lazy<std::false_type>
515 >::type
516 >::type::template evaluate<T>::type
517 {
518 static_assert(std::is_same<I,std::size_t>::value,"Your compiler is broken and does not support checking for arbitrary index types");
519 };
520
521
522#endif // defined(DOXYGEN) or HAVE_IS_INDEXABLE_SUPPORT
523
524
526}
527#endif
Checks wether a type is convertible to another.
Definition: typetraits.hh:177
@ sameType
True if To and From are the same type.
Definition: typetraits.hh:191
@ exists
True if the conversion exists.
Definition: typetraits.hh:187
@ isTwoWay
Whether the conversion exists in both ways.
Definition: typetraits.hh:189
Checks wether a type is derived from another.
Definition: typetraits.hh:247
@ value
True if Base is a base class of Derived.
Definition: typetraits.hh:258
General type traits class to check whether type is reference or pointer type.
Definition: typetraits.hh:41
Definition of the DUNE_DEPRECATED macro for the case that config.h is not available.
#define DUNE_DEPRECATED_MSG(text)
Mark some entity as deprecated.
Definition: deprecated.hh:169
Dune namespace.
Definition: alignment.hh:10
STL namespace.
template which always yields a false value
Definition: typetraits.hh:390
static const bool value
always a false value
Definition: typetraits.hh:392
template which always yields a true value
Definition: typetraits.hh:403
static const bool value
always a true value
Definition: typetraits.hh:405
Determines wether a type is const or volatile and provides the unqualified types.
Definition: typetraits.hh:81
const volatile T ConstVolatileType
The const volatile type.
Definition: typetraits.hh:94
T UnqualifiedType
The unqualified type.
Definition: typetraits.hh:90
@ isConst
True if T has a const qualifier.
Definition: typetraits.hh:86
@ isVolatile
True if T has a volatile specifier.
Definition: typetraits.hh:84
const T ConstType
The const type.
Definition: typetraits.hh:92
Just an empty class.
Definition: typetraits.hh:27
Enable typedef if two types are interoperable.
Definition: typetraits.hh:292
Tests wether a type is constant.
Definition: typetraits.hh:144
@ value
True if The type is constant.
Definition: typetraits.hh:147
Checks wether two types are interoperable.
Definition: typetraits.hh:272
@ value
True if either a conversion from T1 to T2 or vice versa exists.
Definition: typetraits.hh:278
Tests wether a type is volatile.
Definition: typetraits.hh:134
@ value
True if The type is volatile.
Definition: typetraits.hh:137
Definition: typetraits.hh:438
Determine whether a type is a lvalue reference type.
Definition: typetraits.hh:329
is_pointer
Definition: typetraits.hh:314
Return the type a pointer type points to.
Definition: typetraits.hh:347
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