std::is_placeholder
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| Déclaré dans l'en-tête <functional>
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| template< class T > struct is_placeholder; |
(depuis C++11) | |
Si
T est le type d'un espace réservé standard (_1, _2, _3, ...), puis ce modèle est dérivé de std::integral_constant<int,1>, std::integral_constant<int,2>, std::integral_constant<int,3>, respectivement. Si T n'est pas un type d'espace réservé standard, ce modèle est dérivé de std::integral_constant<int,0> .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.
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Le modèle peut être spécialisé pour tout type défini par l'utilisateur qui doit être traitée par std::bind comme s'il s'agissait d'un espace réservé pour les arguments non liés .
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.
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Sommaire |
Inherited from std::integral_constant
Member constants
| value [ statique ]Original: static The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
placeholder value or 0 for non-placeholder types (constante membre statique publique) |
Member functions
| operator int |
convertit l'objet en int, retourne 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. (fonction membre publique) |
Member types
| Type d'
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
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int
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type
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std::integral_constant<int, value> |
[modifier] Exemple
#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'; }
Résultat :
Standard placeholder _5 is for the argument number 5 Adding 2 to 11 selected with a custom placeholder gives 13
[modifier] Voir aussi
| (C++11) |
liaison de paramètres et application partielle d'un foncteur (fonction générique) |
| (C++11) |
placeholders (numéros de paramètre) pour les std::bind (constante) |
