Espaces de noms
Variantes
Affichages
Actions

std::common_type

De cppreference.com
< cpp‎ | types

 
 
 
Soutien aux types fondamentaux
Les types de base
Original:
Basic types
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Types fondamentaux
Fixe les types entiers largeur (C++11)
Limites numériques
Original:
Numeric limits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
numeric_limits
C numérique limite interface
Informations sur le type d'exécution
Original:
Runtime type information
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Caractères de type
Original:
Type traits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Catégories de type primaire
Original:
Primary type categories
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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)
Les propriétés du type
Original:
Type properties
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_const (C++11)
is_volatile (C++11)
is_pod (C++11)
is_empty (C++11)
is_polymorphic (C++11)
is_abstract (C++11)
Opérations prises en charge
Original:
Supported operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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)
Les relations et les requêtes de propriété
Original:
Relationships and property queries
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_same (C++11)
is_base_of (C++11)
is_convertible (C++11)
alignment_of (C++11)
rank (C++11)
extent (C++11)
Modifications de type
Original:
Type modifications
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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)
Transformations de type
Original:
Type transformations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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)
Tapez constantes traits
Original:
Type trait constants
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
integral_constant (C++11)
 
Defined in header <type_traits>
template< class... T >
struct common_type;
(depuis C++11)
Détermine le type commun entre tous les types T..., qui est du type tout T... peut être implicitement converti à .
Original:
Determines the common type among all types T..., that is the type all T... can be implicitly converted to.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
  • std::common_type peut être spécialisé pour les types personnalisés, par exemple std::chrono::time_point .
    Original:
    std::common_type may be specialized for custom types, e.g. std::chrono::time_point.
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
  • Pour les non-spécialisée std::common_type, les règles de détermination du type commun entre chaque paire T1, T2 sont exactement les règles servant à déterminer le type de retour de la opérateur conditionnel ternaireT1 et T2 sont les types de son deuxième et les opérandes tiers .
    Original:
    For non-specialized std::common_type, the rules for determining the common type between every pair T1, T2 are exactly the rules for determining the return type of the opérateur conditionnel ternaire where T1 and T2 are the types of its second and the third operands.
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
  • Pour les types arithmétiques, le type commun peut aussi être considéré comme le type de l'expression arithmétique (éventuellement en mode mixte) tels que T0() + T1() + ... + Tn() .
    Original:
    For arithmetic types, the common type may also be viewed as the type of the (possibly mixed-mode) arithmetic expression such as T0() + T1() + ... + Tn().
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.

Sommaire

[modifier] Types de membres

Nom
Original:
Name
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Definition
type
le type commun à tous T...
Original:
the common type for all T...
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifier] Spécialisations

Spécialisations personnalisés de ce trait de type std::common_type sont autorisés. Les spécialisations suivantes sont déjà fournis par la bibliothèque standard:
Original:
Custom specializations of the type trait std::common_type are allowed. The following specializations are already provided by the standard library:
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
se spécialise trait std::common_type
Original:
specializes the std::common_type trait
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(classe générique spécialisée) [edit]
se spécialise trait std::common_type
Original:
specializes the std::common_type trait
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(classe générique spécialisée) [edit]

[modifier] Notes

Avec un argument de modèle unique, std::common_type<T>::type est exactement T, ce qui rend le C + + équivalent de boost::identity<T>
Original:
With a single template argument, std::common_type<T>::type is exactly T, which makes it the C++ equivalent of boost::identity<T>
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifier] Mise en œuvre possible

template<class ...T> struct common_type;
 
template<class T>
struct common_type<T> {
    typedef T type;
};
 
template<class T, class U>
struct common_type<T, U> {
    typedef decltype(true ? declval<T>() : declval<U>()) type;
};
 
template<class T, class U, class... V>
struct common_type<T, U, V...> {
    typedef typename common_type<typename common_type<T, U>::type, V...>::type type;
};

[modifier] Exemple

Démontre en mode mixte arithmétique sur une classe définie par l'utilisateur
Original:
Demonstrates mixed-mode arithmetic on a user-defined class
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <iostream>
#include <type_traits>
 
template<class T>
struct Number { T n; };
 
template<class T, class U>
Number<typename std::common_type<T, U>::type> operator+(const Number<T>& lhs,
                                                        const Number<U>& rhs) 
{
    return {lhs.n + rhs.n};
}
 
int main()
{
    Number<int> i1 = {1}, i2 = {2};
    Number<double> d1 = {2.3}, d2 = {3.5};
    std::cout << "i1i2: " << (i1 + i2).n << "\ni1d2: " << (i1 + d2).n << '\n'
              << "d1i2: " << (d1 + i2).n << "\nd1d2: " << (d1 + d2).n << '\n';
}

Résultat :

i1i2: 3
i1d2: 4.5
d1i2: 4.3
d1d2: 5.8