close
Namensräume
Varianten

    std::is_placeholder

    Aus cppreference.com
    Image

    This page has been machine-translated from the English version of the wiki using Google Translate.

    The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

    Click here for the English version of this page

    <metanoindex/>

     
    C++
     
    Utilities-Bibliothek
     
    Function-Objekte
    Funktionswrapper
    function(C++11)
    mem_fn(C++11)
    bad_function_call(C++11)
    Bindung
    bind(C++11)
    is_bind_expression(C++11)
    is_placeholder(C++11)
    _1, _2, _3, ...(C++11)
    Referenzwrapper
    reference_wrapper(C++11)
    ref
    cref    		(C++11)
    (C++11)
    Operatorwrapper
    Verneinung
    Veraltete Binder und Adapter
    unary_function(veraltet)
    binary_function(veraltet)
    ptr_fun(veraltet)
    pointer_to_unary_function(veraltet)
    pointer_to_binary_function(veraltet)
    mem_fun(veraltet)
    mem_fun_t
    mem_fun1_t
    const_mem_fun_t
    const_mem_fun1_t    		(veraltet)
    (veraltet)
    (veraltet)
    (veraltet)
    mem_fun_ref(veraltet)
    mem_fun_ref_t
    mem_fun1_ref_t
    const_mem_fun_ref_t
    const_mem_fun1_ref_t    		(veraltet)
    (veraltet)
    (veraltet)
    (veraltet)
    binder1st
    binder2nd    		(veraltet)
    (veraltet)
    bind1st
    bind2nd    		(veraltet)
    (veraltet)
     
    <tbody> </tbody>
    definiert in Header <functional>
    template< class T > struct is_placeholder;
    		 (seit C++11)
    Wenn T der Typ einer Standard-Platzhalter (_1, _2, _3, ...) ist, dann ist diese Vorlage aus std::integral_constant<int,1>, std::integral_constant<int,2>, std::integral_constant<int,3> bzw. abgeleitet. Wenn T kein Standard Platzhalter Art wird diese Vorlage aus std::integral_constant<int,0> abgeleitet .
    Original:
    If T is the type of a standard placeholder (_1, _2, _3, ...), then this template is derived from std::integral_constant<int,1>, std::integral_constant<int,2>, std::integral_constant<int,3>, respectively. If T is not a standard placeholder type, this template is derived from std::integral_constant<int,0>.
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
    Die Schablone kann für jeden Benutzer-definierten Art, die durch std::bind behandelt werden, als ob es ein Platzhalter für ungebundene Argumente war spezialisiert sein .
    Original:
    The template may be specialized for any user-defined type which should be treated by std::bind as if it was a placeholder for unbound arguments.
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.

    Inherited from std::integral_constant

    Member constants

    value
    [statisch]
    		 placeholder value or 0 for non-placeholder types
    (public static Mitglied konstanten)

    Member functions

    operator int
    wandelt das Objekt int, gibt value
    Original:
    converts the object to int, returns value
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.

    (öffentliche Elementfunktion)

    Member types

    Type
    Original:
    Type
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
    		 Definition
    value_type int
    type std::integral_constant<int, value>

    Beispiel

    #include <iostream>
#include <type_traits>
#include <functional>

struct My_2 {
} my_2;

namespace std {
    template<>
    struct is_placeholder<My_2> : public integral_constant<int, 2> {};
}

int f(int n1, int n2)
{
    return n1+n2;
}

int main()
{
    std::cout << "Standard placeholder _5 is for the argument number "
              << std::is_placeholder<decltype(std::placeholders::_5)>::value
              << '\n';

    auto b = std::bind(f, my_2, 2);
    std::cout << "Adding 2 to 11 selected with a custom placeholder gives " 
              << b(10, 11) 
              << '\n';
}

    Output: 

    Standard placeholder _5 is for the argument number 5
Adding 2 to 11 selected with a custom placeholder gives 13

    Siehe auch

    (C++11)
    bindet ein oder mehrere Argumente an eine Funktion Objekt
    Original:
    binds one or more arguments to a function object
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.

    (Funktions-Template) [edit]
    (C++11)
    Platzhalter für den ungebundenen Argumente in einer std::bind Ausdruck
    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.

    (konstanten) [edit]