Class template

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[modifier] Syntaxe

[modifier] Explication

[modifier] Paramètre de modèle non type

• type intégral

  Original:

  integral type

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• énumération

  Original:

  enumeration

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• pointeur à l'objet ou à la fonction

  Original:

  pointer to object or to function

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• référence lvalue pour objet ou pour fonctionner

  Original:

  lvalue reference to object or to function

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• pointeur vers l'objet membre ou un membre de fonction

  Original:

  pointer to member object or to member function

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• std::nullptr_t (depuis C++11)

[modifier] Tapez paramètre de modèle

[modifier] Paramètre template template

[modifier] Instanciation du modèle de classe

[modifier] Instanciation explicite

[modifier] Instanciation implicite

template<class T> struct Z {
    void f() {}
    void g(); // never defined
}; // template definition
template struct Z<double>; // explicit instantiation of Z<double>
Z<int> a; // implicit instantiation of Z<int>
Z<char>* p; // nothing is instantiated here
p->f(); // implicit instantiation of Z<char> and Z<char>::f() occurs here.
// Z<char>::g() is never needed and never instantiated: it does not have to be defined

[modifier] Les paramètres des modèles non-type

• Pour les types entiers et le calcul, l'argument modèle fourni lors de l'instanciation doit être une expression constante .

  Original:

  For integral and arithmetic types, the template argument provided during instantiation must be a constant expression.

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• Pour les pointeurs vers les objets, les arguments de modèle doivent désigner l'adresse d'un objet avec la durée de stockage statique et un lien (interne ou externe), ou une expression constante qui renvoie la valeur de pointeur null approprié .

  Original:

  For pointers to objects, the template arguments have to designate the address of an object with static storage duration and a linkage (either internal or external), or a constant expression that evaluates to the appropriate null pointer value.

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• Pour les pointeurs vers les fonctions, les arguments valides sont des pointeurs vers des fonctions avec liens (ou des expressions constantes qui permettent d'évaluer la valeur null valeurs de pointeur) .

  Original:

  For pointers to functions, the valid arguments are pointers to functions with linkage (or constant expressions that evaluate to null pointer values).

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• Pour les paramètres de référence lvalue, l'argument fourni à l'instanciation ne peut pas être une mesure temporaire, un anonyme lvalue, ou un nom lvalue sans lien .

  Original:

  For lvalue reference parameters, the argument provided at instantiation cannot be a temporary, an unnamed lvalue, or a named lvalue with no linkage.

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• Pour des pointeurs vers les membres, l'argument doit être un pointeur vers le membre exprimée en &Class::Member ou une expression constante qui prend la valeur null valeur de pointeur .

  Original:

  For pointers to members, the argument has to be a pointer to member expressed as &Class::Member or a constant expression that evaluates to null pointer value.

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[modifier] Exemple

template<typename T>
struct S {
    template<typename U> void foo(){}
};
 
template<typename T>
void bar()
{
    S<T>s;
    s.foo<T>(); // error: < parsed as less than operator
    s.template foo<T>(); // OK
}

[modifier] Les paramètres des modèles non-type

#include <iostream>
 
// simple non-type template parameter
template<int N>
struct S {
    int a[N];
};
 
template<const char*>
struct S2 {};
 
// complicated non-type example
template <
    char c, // integral type
    int (&ra)[5], // lvalue reference to object (of array type)
    int (*pf)(int), // pointer to function
    int (S<10>::*a)[10] // pointer to member object (of type int[10])
> struct Complicated {
    // calls the function selected at compile time
    // and stores the result in the array selected at compile time
    void foo(char base) {
        ra[4] = pf(c - base);
    }
};
 
//  S2<"fail"> s2; // Error: string literal cannot be used
char okay[] = "okay"; // static object with linkage
// S2< &okay[0] > s2; // Error: array element has no linkage
S2<okay> s2; // works
 
int a[5];
int f(int n) { return n;}
int main()
{
    S<10> s; // s.a is an array of 10 int
    s.a[9] = 4;
 
    Complicated<'2', a, f, &S<10>::a> c;
    c.foo('0');
 
    std::cout << s.a[9] << a[4] << '\n';
}

42

[modifier] Voir aussi

• <div class="t-tr-text"> déclaration modèle de fonction

  Original:

  function template declaration

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  déclare un modèle de fonction
  Original:

  déclaration modèle de fonction

  Original:

  function template declaration

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  </div> declares a function template

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• <div class="t-tr-text"> spécialisation de template

  Original:

  template specialization

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  définit un modèle existant pour un type particulier
  Original:

  spécialisation de template

  Original:

  template specialization

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  </div> defines an existing template for a specific type

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• <div class="t-tr-text"> paquets de paramètres

  Original:

  parameter packs

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  permet l'utilisation de listes de types de modèles (depuis C++11)
  Original:

  paquets de paramètres

  Original:

  parameter packs

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  </div> allows the use of lists of types in templates (depuis C++11)

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