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std::conditional

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< cpp‎ | types
 
 
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Operadores relacionales
Original:
Relational operators
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Pairs and tuples
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Cambiar, hacia adelante y mover
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Swap, forward and move
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Tipos básicos
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Basic types
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Tipos fundamentales
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Límites numéricos
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Numeric limits
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Información de tipo en tiempo de ejecución
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Runtime type information
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Caracteres de tipo
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Type traits
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Categorías primarias de tipo
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Primary type categories
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Propiedades de tipo
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Type properties
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Operaciones compatibles
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Supported operations
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Relaciones y consultas de propiedad
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Relationships and property queries
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Modificaciones de tipo
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Type modifications
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Transformaciones de tipo
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Type transformations
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conditional
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Type trait constants
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Definido en la cabecera <type_traits>
template< bool B, class T, class F >
struct conditional;
(desde C++11)
Proporciona type miembro typedef, que se define como T si B es true en tiempo de compilación, o como si F B es false .
Original:
Provides member typedef type, which is defined as T if B is true at compile time, or as F if B is false.
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Contenido

[editar] Tipos de miembros

Miembro de tipo
Original:
Member type
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Definition
type T if B == true, F if B == false

[editar] Posible implementación

template<bool B, class T, class F>
struct conditional { typedef T type; };
 
template<class T, class F>
struct conditional<false, T, F> { typedef F type; };

[editar] Ejemplo

#include <iostream>
#include <type_traits>
#include <typeinfo>
 
int main() 
{
    typedef std::conditional<true, int, double>::type Type1;
    typedef std::conditional<false, int, double>::type Type2;
    typedef std::conditional<sizeof(int) >= sizeof(double), int, double>::type Type3;
 
    std::cout << typeid(Type1).name() << '\n';
    std::cout << typeid(Type2).name() << '\n';
    std::cout << typeid(Type3).name() << '\n';
}

Salida:

i
d
d

[editar] Ver también

(C++11)
esconde una sobrecarga de la función o especialización plantilla basada en booleana en tiempo de compilación
Original:
hides a function overload or template specialization based on compile-time boolean
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(plantilla de clase) [editar]