std::is_copy_constructible, std::is_trivially_copy_constructible, std::is_nothrow_copy_constructible – cppreference.com

std::is_copy_constructible, std::is_trivially_copy_constructible, std::is_nothrow_copy_constructible

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C++
 
Utilities-Bibliothek
 
Geben Sie Unterstützung
Grundtypen
Original:
Basic types
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Grundtypen
Feste Breite Integer-Typen (C++11)
Numerische Grenzen
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Numeric limits
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numeric_limits
C numerische begrenzt Schnittstelle
Laufzeit-Typinformationen
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Runtime type information
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Exterieur
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Type traits
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Primären Typ Kategorien
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Primary type categories
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is_void(C++11)
is_array(C++11)
is_pointer(C++11)
is_enum(C++11)
is_union(C++11)
is_class(C++11)
is_function(C++11)
is_object(C++11)
is_scalar(C++11)
is_compound(C++11)
is_integral(C++11)
is_floating_point(C++11)
is_fundamental(C++11)
is_arithmetic(C++11)
is_reference(C++11)
is_lvalue_reference(C++11)
is_rvalue_reference(C++11)
is_member_pointer(C++11)
is_member_object_pointer(C++11)
is_member_function_pointer(C++11)
Typ Eigenschaften
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Type properties
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is_const(C++11)
is_volatile(C++11)
is_pod(C++11)
is_empty(C++11)
is_polymorphic(C++11)
is_abstract(C++11)
Unterstützte Operationen
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Supported operations
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is_constructible
is_trivially_constructible
is_nothrow_constructible		(C++11)
(C++11)
(C++11)
is_default_constructible
is_trivially_default_constructible
is_nothrow_default_constructible		(C++11)
(C++11)
(C++11)
is_copy_constructible
is_trivially_copy_constructible
is_nothrow_copy_constructible		(C++11)
(C++11)
(C++11)
is_move_constructible
is_trivially_move_constructible
is_nothrow_move_constructible		(C++11)
(C++11)
(C++11)
is_assignable
is_trivially_assignable
is_nothrow_assignable		(C++11)
(C++11)
(C++11)
is_copy_assignable
is_trivially_copy_assignable
is_nothrow_copy_assignable		(C++11)
(C++11)
(C++11)
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable		(C++11)
(C++11)
(C++11)
is_destructible
is_trivially_destructible
is_nothrow_destructible		(C++11)
(C++11)
(C++11)
has_virtual_destructor(C++11)
Beziehungen und Eigentum Abfragen
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Relationships and property queries
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is_same(C++11)
is_base_of(C++11)
is_convertible(C++11)
alignment_of(C++11)
rank(C++11)
extent(C++11)
Typ Modifikationen
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Type modifications
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remove_cv
remove_const
remove_volatile		(C++11)
(C++11)
(C++11)
add_cv
add_const
add_volatile		(C++11)
(C++11)
(C++11)
make_signed(C++11)
make_unsigned(C++11)
Typ Transformationen
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Type transformations
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aligned_storage(C++11)
aligned_union(C++11)
decay(C++11)
enable_if(C++11)
conditional(C++11)
common_type(C++11)
underlying_type(C++11)
result_of(C++11)
Typ-Trait-Konstanten
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Type trait constants
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integral_constant(C++11)
 
<tbody> </tbody>
definiert in Header <type_traits>
template< class T > struct is_copy_constructible;
 (1) (seit C++11)
template< class T > struct is_trivially_copy_constructible;
 (2) (seit C++11)
template< class T > struct is_nothrow_copy_constructible;
 (3) (seit C++11)

1)

Prüft, ob eine Art CopyConstructible ist, dh eine zugängliche explizite oder implizite Copy-Konstruktor. Wenn die Bedingung erfüllt ist, ein Mitglied konstanten value gleich true bereitgestellt wird, sonst value ist false .
Original:
Checks whether a type is CopyConstructible, i.e. has an accessible explicit or implicit copy constructor. If the requirement is met, a member constant value equal true is provided, otherwise value is false.
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2)

Same as (1), aber die Kopie Konstruktor Ausdruck nicht nennen jede Operation, die nicht trivial ist .
Original:
Same as (1), but the copy constructor expression does not call any operation that is not trivial.
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3)

Same as (1), aber die Kopie Konstruktor Ausdruck noexcept .
Original:
Same as (1), but the copy constructor expression is noexcept.
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Inherited from std::integral_constant

Member constants

value
[statisch]
true wenn T is copy-constructible , false anders
Original:
true if T is copy-constructible , false otherwise
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(public static Mitglied konstanten)

Member functions

operator bool
wandelt das Objekt bool, gibt value
Original:
converts the object to bool, returns value
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(öffentliche Elementfunktion)

Member types

Type
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Type
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 Definition
value_type bool
type std::integral_constant<bool, value>

Mögliche Implementierung

template<class T>
struct is_copy_constructible :
    std::is_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

template<class T>
struct is_trivially_copy_constructible :
    std::is_trivially_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

template<class T>
struct is_nothrow_copy_constructible :
    std::is_nothrow_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

Beispiel

#include <iostream>
#include <type_traits>

struct Ex1 {
    std::string str; // member has a non-trivial copy ctor
};
struct Ex2 {
    int n;
    Ex2(const Ex2&) = default; // trivial and non-throwing
};

int main() {
    std::cout << std::boolalpha << "Ex1 is copy-constructible? "
              << std::is_copy_constructible<Ex1>::value << '\n'
              << "Ex1 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex1>::value << '\n'
              << "Ex2 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex2>::value << '\n'
              << "Ex2 is nothrow copy-constructible? "
              << std::is_nothrow_copy_constructible<Ex2>::value << '\n';
}

Output: 

Ex1 is copy-constructible? true
Ex1 is trivially copy-constructible? false
Ex2 is trivially copy-constructible? true
Ex2 is nothrow copy-constructible? true

Siehe auch