Varianti

    std::is_pointer

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    <metanoindex/>

     
    C++
     
    Utilità libreria
    Tipo di supporto (basic types, RTTI, type traits)
    Gestione della memoria dinamica
    La gestione degli errori
    Programma di utilità
    Funzioni variadic
    Data e ora
    Funzione oggetti
    initializer_list(C++11)
    bitset
    hash(C++11)
    Gli operatori relazionali
    Original:
    Relational operators
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    rel_ops::operator!=
    rel_ops::operator>
    rel_ops::operator<=
    rel_ops::operator>=
    Coppie e tuple
    Original:
    Pairs and tuples
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    pair
    tuple(C++11)
    piecewise_construct_t(C++11)
    piecewise_construct(C++11)
    Swap, in avanti e spostare
    Original:
    Swap, forward and move
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    swap
    forward(C++11)
    move(C++11)
    move_if_noexcept(C++11)
    declval(C++11)
     
    Tipo di supporto
    Tipi base
    Original:
    Basic types
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    Tipi fondamentali
    Larghezza fissa interi tipi (C++11)
    Limiti numerici
    Original:
    Numeric limits
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    numeric_limits
    C numerico limita interfaccia
    Informazioni sul tipo di runtime
    Original:
    Runtime type information
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    Tipo tratti
    Original:
    Type traits
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    Categorie di tipo primario
    Original:
    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)
    Proprietà del tipo
    Original:
    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)
    Operazioni supportate
    Original:
    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)
    I rapporti e le query di proprietà
    Original:
    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)
    Tipo modifiche
    Original:
    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)
    Tipo di trasformazioni
    Original:
    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)
    Digitare costanti tratto
    Original:
    Type trait constants
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    integral_constant(C++11)
     
    <tbody> </tbody>
    Elemento definito nell'header <type_traits>
    template< class T > struct is_pointer;
    		 (dal C++11)
    Se T è un tipo di puntatore oggetto o un tipo di puntatore a funzione (ma non puntatore non statico oggetto membro o funzione membro), fornisce la costante value true uguale membro. Per qualsiasi altro tipo, è value false.
    Original:
    If T is an object pointer type or a function pointer type (but not pointer to non-static member object or member function), provides the member constant value equal true. For any other type, value is false.
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    Inherited from std::integral_constant

    Member constants

    value
    [statico]
    true se T is a pointer type , false altrimenti
    Original:
    true if T is a pointer type , false otherwise
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    (pubblico membro statico costante)

    Member functions

    operator bool
    converte l'oggetto in bool, restituisce value
    Original:
    converts the object to bool, returns value
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    (metodo pubblico)

    Member types

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

    Possibile implementazione

    template< class T > struct is_pointer_helper     : std::false_type {};
template< class T > struct is_pointer_helper<T*> : std::true_type {};
template< class T > struct is_pointer : is_pointer_helper<typename std::remove_cv<T>::type> {};

    Esempio

    #include <iostream>
#include <type_traits>

class A {};

int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_pointer<A>::value << '\n';
    std::cout << std::is_pointer<A*>::value << '\n';
    std::cout << std::is_pointer<float>::value << '\n';
    std::cout << std::is_pointer<int>::value << '\n';
    std::cout << std::is_pointer<int*>::value << '\n';
    std::cout << std::is_pointer<int**>::value << '\n';
}

    Output: 

    false
true
false
false
true
true

    Vedi anche

    (C++11)
    Verifica se un tipo è un tipo di matrice
    Original:
    checks if a type is an array type
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    (classe template) [modifica]
    (C++11)
    Verifica se un tipo è di tipo scalare
    Original:
    checks if a type is scalar type
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    (classe template) [modifica]