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std::ptrdiff_t

Da cppreference.com.
< cpp‎ | types

 
 
Utilità libreria
Tipo di supporto (basic types, RTTI, type traits)
Gestione della memoria dinamica
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Programma di utilità
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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
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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
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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
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Basic types
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Tipi fondamentali
Larghezza fissa interi tipi (C++11)
ptrdiff_t
size_t
max_align_t(C++11)
Limiti numerici
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Numeric limits
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numeric_limits
C numerico limita interfaccia
Informazioni sul tipo di runtime
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Runtime type information
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Tipo tratti
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Categorie di tipo primario
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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
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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)
Operazioni supportate
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Supported operations
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is_constructible
is_trivially_constructible
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(C++11)
(C++11)
(C++11)
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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
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(C++11)
(C++11)
(C++11)
is_assignable
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(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
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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)
Tipo modifiche
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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)
Tipo di trasformazioni
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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
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Type trait constants
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integral_constant(C++11)
 
Defined in header <cstddef>
typedef /*implementation-defined*/ ptrdiff_t;
std::ptrdiff_t è il tipo intero con segno del risultato della sottrazione dei due puntatori.
Original:
std::ptrdiff_t is the signed integer type of the result of subtracting two pointers.
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[modifica] Note

std::ptrdiff_t è utilizzato per l'aritmetica dei puntatori e l'indicizzazione di array, se i valori negativi sono possibili. Programmi che utilizzano altri tipi, come int, può fallire su, ad esempio Sistemi a 64 bit, quando l'indice supera INT_MAX o se si basa su 32 bit aritmetica modulare.
Original:
std::ptrdiff_t is used for pointer arithmetic and array indexing, if negative values are possible. Programs that use other types, such as int, may fail on, e.g. 64-bit systems when the index exceeds INT_MAX or if it relies on 32-bit modular arithmetic.
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Quando si lavora con il C + + contenitore di libreria, il tipo corretto per la differenza tra gli iteratori è il difference_type membro typedef, che spesso è sinonimo di std::ptrdiff_t.
Original:
When working with the C++ container library, the proper type for the difference between iterators is the member typedef difference_type, which is often synonymous with std::ptrdiff_t.
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Solo i puntatori alle elementi della matrice stessa (compreso il puntatore uno oltre la fine della matrice) possono essere sottratti tra loro.
Original:
Only pointers to elements of the same array (including the pointer one past the end of the array) may be subtracted from each other.
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Se un array è così grande (maggiore di elementi PTRDIFF_MAX, ma meno di SIZE_MAX byte), che la differenza tra due puntatori non possono essere rappresentabile come std::ptrdiff_t, il risultato della sottrazione tali due puntatori è indefinito.
Original:
If an array is so large (greater than PTRDIFF_MAX elements, but less than SIZE_MAX bytes), that the difference between two pointers may not be representable as std::ptrdiff_t, the result of subtracting two such pointers is undefined.
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Per gli array char di lunghezza inferiore a PTRDIFF_MAX, std::ptrdiff_t funge da controparte firmata std::size_t: è in grado di memorizzare le dimensioni della matrice di qualsiasi tipo ed è, sulla maggior parte delle piattaforme, sinonimo di std::intptr_t).
Original:
For char arrays shorter than PTRDIFF_MAX, std::ptrdiff_t acts as the signed counterpart of std::size_t: it can store the size of the array of any type and is, on most platforms, synonymous with std::intptr_t).
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[modifica] Esempio

#include <cstddef>
int main()
{
    const std::size_t N = 100;
    int* a = new int[N];
    int* end = a + N;
    for(std::ptrdiff_t i = N; i>0; --i)
        *(end - i) = i;
    delete[] a;
 
}


[modifica] Vedi anche

senza segno tipo intero restituito dal gestore sizeof
Original:
unsigned integer type returned by the sizeof operator
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(typedef) [edit]
byte offset dall'inizio di un layout di tipo standard per membro specificato
Original:
byte offset from the beginning of a standard-layout type to specified member
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(funzione macro) [edit]