Namespace
Varianti

std::bind

Da cppreference.com.
< cpp‎ | utility‎ | functional


 
 
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
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Coppie e tuple
Original:
Pairs and tuples
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Swap, in avanti e spostare
Original:
Swap, forward and move
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
Funzione oggetti
Funzione wrapper
Original:
Function wrappers
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
function(C++11)
mem_fn(C++11)
bad_function_call(C++11)
Associare
Original:
Bind
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
bind(C++11)
is_bind_expression(C++11)
is_placeholder(C++11)
_1, _2, _3, ...(C++11)
Wrapper di riferimento
Original:
Reference wrappers
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
reference_wrapper(C++11)
ref
cref
(C++11)
(C++11)
Operatore wrapper
Original:
Operator wrappers
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Negatori
Original:
Negators
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Sconsigliata a leganti e adattatori
Original:
Deprecated binders and adaptors
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unary_function(deprecato)
binary_function(deprecato)
ptr_fun(deprecato)
pointer_to_unary_function(deprecato)
pointer_to_binary_function(deprecato)
mem_fun(deprecato)
mem_fun_t
mem_fun1_t
const_mem_fun_t
const_mem_fun1_t
(deprecato)
(deprecato)
(deprecato)
(deprecato)
mem_fun_ref(deprecato)
mem_fun_ref_t
mem_fun1_ref_t
const_mem_fun_ref_t
const_mem_fun1_ref_t
(deprecato)
(deprecato)
(deprecato)
(deprecato)
binder1st
binder2nd
(deprecato)
(deprecato)
bind1st
bind2nd
(deprecato)
(deprecato)
 
Defined in header <functional>
template< class F, class... Args >
/*unspecified*/ bind( F&& f, Args&&... args );
(1) (dal C++11)
template< class R, class F, class... Args >
/*unspecified*/ bind( F&& f, Args&&... args );
(2) (dal C++11)
La bind modello di funzione genera un wrapper per la deviazione di chiamata f. La chiamata a questo involucro è equivalente a invocare f con alcuni dei suoi argomenti legati alla args.
Original:
The function template bind generates a forwarding call wrapper for f. Calling this wrapper is equivalent to invoking f with some of its arguments bound to args.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Internamente, l'involucro contiene un oggetto membro del std::decay<F>::type tipo costruito da std::forward<F>(f), e un oggetto per ciascuna delle args..., di std::decay<Arg_i>::type tipo, analogamente costruito std::forward<Arg_i>(arg_i).
Original:
Internally, the wrapper holds a member object of type std::decay<F>::type constructed from std::forward<F>(f), and one object per each of args..., of type std::decay<Arg_i>::type, similarly constructed from std::forward<Arg_i>(arg_i).
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Indice

[modifica] Parametri

f -
oggetto invocabile (oggetto funzione, puntatore a funzione, il riferimento alla funzione, puntatore a funzione membro, o il puntatore ai dati membri), che dovrà essere associata ad alcuni argomenti
Original:
invocable object (function object, pointer to function, reference to function, pointer to member function, or pointer to member data) that will be bound to some arguments
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
args -
elenco di argomenti di legare, con gli argomenti non legati sostituiti dal _1, _2, _3... segnaposto
Original:
list of arguments to bind, with the unbound arguments replaced by the placeholders _1, _2, _3...
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifica] Valore di ritorno

Un oggetto funzione di T tipo specificato, per cui std::is_bind_expression<T>::value == true, e che possono essere memorizzati in std::function. L'oggetto è mobile se f e tutti args sono mobili, ed è copiabile altrimenti. Il tipo definisce i seguenti membri:
Original:
A function object of unspecified type T, for which std::is_bind_expression<T>::value == true, and which can be stored in std::function. The object is movable if f and all args are movable, and is copyable otherwise. The type defines the following members:
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

std :: bind
Original:
std::bind
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Return type

Member type result_type

1) If F is a pointer to function or a pointer to member function, result_type is the return type of F. If F is a class type with nested typedef result_type, then result_type is F::result_type. Otherwise no result_type is defined.

2) result_type is exactly R.

Member function operator()

Given an object g obtained from an earlier call to bind, when it is invoked in a function call expression g(u1, u2, ... uM), an invocation of the stored object of type std::decay<F>::type takes place, with arguments defined as follows:

  • If the argument is of type std::reference_wrapper<T> (e.g. std::ref or std::cref) was used in the initial call to bind, then the reference T& stored in the bound argument is passed to the invocable object.
  • If std::is_bind_expression<T>::value == true (i.e. another sbind subexpression was used as an argument in the initial call to bind), then that bind-subexpressin is invoked immediately and its result is passed to the invocable object. If the bind subexpression has any placeholder arguments, they are picked from u1, u2, ....
  • If std::is_placeholder<T>::value != 0 (i.e., _1, _2, _3, ... was used as the argument to the initial call to bind), then the argument indicated by the placeholder (u1 for _1, u2 for _2, etc) is passed to the invocable object as std::forward<Uj>(uj).
  • Otherwise, the stored argument is passed to the invocable object as-is.

If some of the arguments that are supplied in the call to g() are not matched by any placeholders stored in g, the unused arguments are evaluated and discarded.

[modifica] Eccezioni

Genera solo se la costruzione std::decay<F>::type da std::forward<F>(f) getta, o uno dei costruttori per std::decay<Arg_i>::type dal std::forward<Arg_i>(arg_i) corrsponding getta dove Arg_i è il tipo i-esimo e arg_i è l'argomento-esimo in Args... args.
Original:
Only throws if construction of std::decay<F>::type from std::forward<F>(f) throws, or any of the constructors for std::decay<Arg_i>::type from the corrsponding std::forward<Arg_i>(arg_i) throws where Arg_i is the ith type and arg_i is the ith argument in Args... args.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifica] Note

Gli argomenti di impegnare vengono copiati o spostati, e non sono mai passati per riferimento se non avvolto in std::ref o std::cref.
Original:
The arguments to bind are copied or moved, and are never passed by reference unless wrapped in std::ref or std::cref.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Duplicare segnaposto nell'espressione stessa bind (più _1 per esempio) sono permessi, ma i risultati sono ben definite solo se l'argomento corrispondente (u1) è un rvalue lvalue o non mobile.
Original:
Duplicate placeholders in the same bind expression (multiple _1's for example) are allowed, but the results are only well defined if the corresponding argument (u1) is an lvalue or non-movable rvalue.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifica] Esempio

#include <random>
#include <iostream>
#include <functional>
 
void f(int n1, int n2, int n3, const int& n4, int n5)
{
    std::cout << n1 << ' ' << n2 << ' ' << n3 << ' ' << n4 << ' ' << n5 << '\n';
}
 
int g(int n1)
{
    return n1;
}
 
struct Foo {
    void print_sum(int n1, int n2)
    {
        std::cout << n1+n2 << '\n';
    }
    int data = 10;
};
 
int main()
{
    using namespace std::placeholders;
 
    // demonstrates argument reordering and pass-by-reference
    int n = 7;
    auto f1 = std::bind(f, _2, _1, 42, std::cref(n), n);
    n = 10;
    f1(1, 2, 1001); // 1 is bound by _1, 2 is bound by _2, 1001 is unused
 
    // nested bind subexpressions share the placeholders
    auto f2 = std::bind(f, _3, std::bind(g, _3), _3, 4, 5);
    f2(10, 11, 12);
 
    // common use case: binding a RNG with a distribution
    std::default_random_engine e;
    std::uniform_int_distribution<> d(0, 10);
    std::function<int()> rnd = std::bind(d, e);
    for(int n=0; n<10; ++n)
        std::cout << rnd() << ' ';
    std::cout << '\n';
 
    // bind to a member function
    Foo foo;
    auto f3 = std::bind(&Foo::print_sum, foo, 95, _1);
    f3(5);
 
    // bind to member data
    auto f4 = std::bind(&Foo::data, _1);
    std::cout << f4(foo) << '\n';
}

Output:

2 1 42 10 7
12 12 12 4 5
1 5 0 2 0 8 2 2 10 8
100
10

[modifica] Vedi anche

segnaposto per gli argomenti non legate in un'espressione std::bind
Original:
placeholders for the unbound arguments in a std::bind expression
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(costante) [edit]
(C++11)
crea un oggetto funzione di un puntatore a un membro
Original:
creates a function object out of a pointer to a member
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(funzione di modello) [edit]