C++ Utilities  5.10.5
Useful C++ classes and routines such as argument parser, IO and conversion utilities
traits.h
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1 #ifndef CPP_UTILITIES_TRAITS_H
2 #define CPP_UTILITIES_TRAITS_H
3 
4 #include <iterator>
5 #include <string>
6 #include <type_traits>
7 
8 namespace CppUtilities {
9 
11 namespace Traits {
12 
14 namespace Detail {
15 enum class Enabler {};
16 }
18 
20 template <typename If, typename Then, typename Else> using Conditional = typename std::conditional<If::value, Then, Else>::type;
21 
23 template <bool B, typename...> struct Bool : std::integral_constant<bool, B> {
24 };
25 
27 template <typename T> using Not = Bool<!T::value>;
28 
30 template <typename... T> struct Any : Bool<false> {
31 };
33 template <typename Head, typename... Tail> struct Any<Head, Tail...> : Conditional<Head, Bool<true>, Any<Tail...>> {
34 };
35 
37 template <typename... T> struct All : Bool<true> {
38 };
40 template <typename Head, typename... Tail> struct All<Head, Tail...> : Conditional<Head, All<Tail...>, Bool<false>> {
41 };
42 
44 template <typename... T> struct None : Bool<true> {
45 };
47 template <typename Head, typename... Tail> struct None<Head, Tail...> : Conditional<Head, Bool<false>, None<Tail...>> {
48 };
49 
51 template <typename... Condition> using EnableIf = typename std::enable_if<All<Condition...>::value, Detail::Enabler>::type;
53 template <typename... Condition> using DisableIf = typename std::enable_if<!All<Condition...>::value, Detail::Enabler>::type;
54 
56 template <typename... Condition> using EnableIfAny = typename std::enable_if<Any<Condition...>::value, Detail::Enabler>::type;
58 template <typename... Condition> using DisableIfAny = typename std::enable_if<!Any<Condition...>::value, Detail::Enabler>::type;
59 
61 namespace Detail {
62 template <typename T, template <typename...> class Template> struct IsSpecializationOfHelper : Bool<false> {
63 };
64 template <template <typename...> class Template, typename... Args> struct IsSpecializationOfHelper<Template<Args...>, Template> : Bool<true> {
65 };
66 } // namespace Detail
69 template <typename Type, template <typename...> class... TemplateTypes>
71  : Detail::IsSpecializationOfHelper<typename std::remove_cv<typename std::remove_reference<Type>::type>::type, TemplateTypes...> {
72 };
74 template <typename Type, template <typename...> class... TemplateTypes> struct IsSpecializingAnyOf : Bool<false> {
75 };
77 template <typename Type, template <typename...> class TemplateType, template <typename...> class... RemainingTemplateTypes>
78 struct IsSpecializingAnyOf<Type, TemplateType, RemainingTemplateTypes...>
79  : Conditional<IsSpecializationOf<Type, TemplateType>, Bool<true>, IsSpecializingAnyOf<Type, RemainingTemplateTypes...>> {
80 };
81 
83 template <typename... T> struct IsAnyOf : Bool<false> {
84 };
86 template <typename Type, typename OtherType, typename... RemainingTypes>
87 struct IsAnyOf<Type, OtherType, RemainingTypes...> : Conditional<std::is_same<Type, OtherType>, Bool<true>, IsAnyOf<Type, RemainingTypes...>> {
88 };
90 template <typename... T> struct IsNoneOf : Bool<true> {
91 };
93 template <typename Type, typename OtherType, typename... RemainingTypes>
94 struct IsNoneOf<Type, OtherType, RemainingTypes...> : Conditional<std::is_same<Type, OtherType>, Bool<false>, IsNoneOf<Type, RemainingTypes...>> {
95 };
96 
98 template <typename T>
99 struct IsCString
100  : Bool<std::is_same<char const *, typename std::decay<T>::type>::value || std::is_same<char *, typename std::decay<T>::type>::value> {
101 };
104 template <typename T>
105 struct IsString
106  : Bool<IsCString<T>::value || IsSpecializationOf<T, std::basic_string>::value || IsSpecializationOf<T, std::basic_string_view>::value> {
107 };
108 
110 template <typename T, typename = void> struct IsComplete : Bool<false> {
111 };
113 template <typename T> struct IsComplete<T, decltype(void(sizeof(T)))> : Bool<true> {
114 };
115 
120 #define CPP_UTILITIES_PP_COMMA ,
121 
128 #define CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(CheckName, CheckCode) \
129  namespace Detail { \
130  template <typename T> auto CheckName(int) -> decltype(CheckCode, ::CppUtilities::Traits::Bool<true>{}); \
131  template <typename T>::CppUtilities::Traits::Bool<false> CheckName(...); \
132  } \
133  template <typename T> using CheckName = decltype(Detail::CheckName<T>(0))
134 
136 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(IsDereferencable, *(std::declval<T &>()));
137 
139 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(HasSize, std::is_integral<decltype(std::declval<T &>().size())>::value);
140 
142 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(IsReservable, std::declval<T &>().reserve(0u));
143 
145 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(IsResizable, std::declval<T &>().resize(0u));
146 
148 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(HasOperatorBool, std::declval<T &>() ? true : false);
149 
152  // begin/end and operator !=
153  std::begin(std::declval<T &>())
154  != std::end(std::declval<T &>()) CPP_UTILITIES_PP_COMMA
155  // operator ,
157  // operator ++
158  ++ std::declval<decltype(begin(std::declval<T &>())) &>() CPP_UTILITIES_PP_COMMA
159  // operator*
160  void(*begin(std::declval<T &>())));
161 
163 template <typename T, EnableIf<IsDereferencable<T>> * = nullptr> constexpr auto &dereferenceMaybe(T &&value)
164 {
165  return *value;
166 }
167 
169 template <typename T, DisableIf<IsDereferencable<T>> * = nullptr> constexpr auto &dereferenceMaybe(T &&value)
170 {
171  return value;
172 }
173 
174 } // namespace Traits
175 
176 } // namespace CppUtilities
177 
178 #endif // CPP_UTILITIES_TRAITS_H
constexpr auto & dereferenceMaybe(T &&value)
Dereferences the specified value if possible; otherwise just returns value itself.
Definition: traits.h:163
CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(IsDereferencable, *(std::declval< T & >()))
Evaluates to Bool<true> if the specified type can be dereferenced using the *-operator; otherwise eva...
typename std::enable_if< All< Condition... >::value, Detail::Enabler >::type EnableIf
Shortcut for std::enable_if to omit ::value and ::type.
Definition: traits.h:51
typename std::enable_if< Any< Condition... >::value, Detail::Enabler >::type EnableIfAny
Shortcut for std::enable_if to apply Traits::Any and omit ::value and ::type.
Definition: traits.h:56
typename std::enable_if<!All< Condition... >::value, Detail::Enabler >::type DisableIf
Shortcut for std::enable_if to negate the condition and omit ::value and ::type.
Definition: traits.h:53
typename std::conditional< If::value, Then, Else >::type Conditional
Shortcut for std::conditional to omit ::value and ::type.
Definition: traits.h:20
typename std::enable_if<!Any< Condition... >::value, Detail::Enabler >::type DisableIfAny
Shortcut for std::enable_if to apply Traits::Any, negate the condition and omit ::value and ::type.
Definition: traits.h:58
Contains all utilities provides by the c++utilities library.
Evaluates to Bool<true> if all specified conditions are true; otherwise evaluates to Bool<false>.
Definition: traits.h:37
Evaluates to Bool<true> if at least one of the specified conditions is true; otherwise evaluates to B...
Definition: traits.h:30
Wraps a static boolean constant.
Definition: traits.h:23
Evaluates to Bool<true> if the specified type is any of the specified types; otherwise evaluates to B...
Definition: traits.h:83
Evaluates to Bool<true> if the specified type is a C-string (char * or const char *); otherwise evalu...
Definition: traits.h:100
Evaluates to Bool<true> if the specified type is complete; if the type is only forward-declared it ev...
Definition: traits.h:110
Evaluates to Bool<true> if the specified type is none of the specified types; otherwise evaluates to ...
Definition: traits.h:90
Evaluates to Bool<true> if the specified type is based on the specified template; otherwise evaluates...
Definition: traits.h:71
Evaluates to Bool<true> if the specified type is based on one of the specified templates; otherwise e...
Definition: traits.h:74
Evaluates to Bool<true> if the specified type is a standard string, standard string view or C-string ...
Definition: traits.h:106
Evaluates to Bool<true> if none of the specified conditions are true; otherwise evaluates to Bool<fal...
Definition: traits.h:44
#define CPP_UTILITIES_PP_COMMA
The CPP_UTILITIES_PP_COMMA macro helps passing "," as a macro argument.
Definition: traits.h:120