explicit type conversion
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Convierte entre distintos tipos utilizando una combinación de conversiones explícitas e implícitas .
Original:
Converts between types using a combination of explicit and implicit conversions.
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[editar] Sintaxis
( new_type ) expression
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new_type ( expression )
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Devuelve un valor de tipo
new_type .Original:
Returns a value of type
new_type.The text has been machine-translated via Google Translate.
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[editar] Explicación
1)
Cuando la expresión de conversión de estilo C se encuentra, el compilador intenta las expresiones de conversión siguientes, en este orden:
Original:
When the C-style cast expression is encountered, the compiler attempts the following cast expressions, in this order:
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a) const_cast<new_type>(expression)
b)
static_cast<new_type>(expression), con extensiones: puntero o una referencia a una clase derivada es, además, permite que se convierte en puntero o referencia a la clase base no ambigua (y viceversa), incluso si la clase base es de difícil acceso (es decir, este elenco ignora la herencia privada especificador) . Lo mismo se aplica a echar puntero a miembro de puntero a miembro de inequívoca de no virtual base
Original:
static_cast<new_type>(expression), with extensions: pointer or reference to a derived class is additionally allowed to be cast to pointer or reference to unambiguous base class (and vice versa) even if the base class is inaccessible (that is, this cast ignores the private inheritance specifier). Same applies to casting pointer to member to pointer to member of unambigous non-virtual base
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c)
static_cast (con extensiones), seguido de const_cast
Original:
static_cast (with extensions) followed by const_cast
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d) reinterpret_cast<new_type>(expression)
e)
reinterpret_cast seguido por const_cast
Original:
reinterpret_cast followed by const_cast
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@ @ La primera opción que satisface los requisitos de la respectiva operador de conversión se selecciona, incluso si no puede ser compilado (véase el ejemplo) .
Original:
@@ The first choice that satisfies the requirements of the respective cast operator is selected, even if it cannot be compiled (see example).
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@ @ Además, C-estilo de notación de conversión se le permite emitir desde, hacia y entre los punteros a tipo de clase incompleto. Si tanto expression y new_type son punteros a tipos de clases incompletas, es indeterminado si static_cast o reinterpret_cast es seleccionado .
Original:
@@ In addition, C-style cast notation is allowed to cast from, to, and between pointers to incomplete class type. If both expression and new_type are pointers to incomplete class types, it's unspecified whether static_cast or reinterpret_cast gets selected.
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2)
El reparto funcional consta de un especificador de tipo simple o un especificador typedef (en otras palabras, una sola palabra Nombre Tipo: unsigned int(expression) o int*(expression) no son válidos), seguido de una sola expresión entre paréntesis. Este reparto es exactamente equivalente a la expresión de conversión correspondiente C-style .
Original:
The functional cast consists of a simple type specifier or a typedef specifier (in other words, a single-word type name: unsigned int(expression) or int*(expression) are not valid), followed by a single expression in parentheses. This cast is exactly equivalent to the corresponding C-style cast expression.
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Como con todas las expresiones de conversión, el resultado es:
Original:
As with all cast expressions, the result is:
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- un valor-si new_type es un tipo de referencia o una referencia de valor-valor-poder funcionar en su tipo;Original:an lvalue if new_type is an lvalue reference type or an rvalue reference to function type;The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions. - un xValue si new_type es una referencia a rvalue tipo de objeto;Original:an xvalue if new_type is an rvalue reference to object type;The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions. - un prvalue de otra manera .Original:a prvalue otherwise.The text has been machine-translated via Google Translate.
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[editar] Ejemplo
double f = 3.14; unsigned int n1 = (unsigned int)f; // C-style cast unsigned int n2 = unsigned(f); // functional cast class C1; class C2; C2* foo(C1* p) { return (C2*)p; // casts incomplete type to incomplete type } // In this example, C-style cast is interpreted as static_cast // even though it would work as reinterpret_cast struct A {}; struct I1 : A {}; struct I2 : A {}; struct D : I1, I2 {}; int main() { D* d = nullptr; A* a = (A*)d; // compile-time error A* a = reinterpret_cast<A*>(d); // this compiles }
