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if statement

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Lenguaje C++
Los temas generales
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General topics
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Control de flujo
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Flow control
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Sentencias condicionales ejecución
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Conditional execution statements
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if statement
Instrucciones de iteración
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Iteration statements
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Ir declaraciones
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Jump statements
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Funciones
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Functions
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declaración de la función
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función de plantilla
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Excepciones
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Exceptions
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Los espacios de nombres
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Namespaces
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Tipos
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Types
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decltype specifier (C++11)
Los especificadores
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cv especificadores
almacenamiento duración especificadores
constexpr especificador (C++11)
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Inicialización
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Initialization
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Los literales
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Literals
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Expresiones
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Expressions
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representaciones alternativas
Utilidades
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Utilities
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Tipos
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Types
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typedef declaration
alias de tipo de declaración (C++11)
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Lanza
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Clases
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Classes
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Clase propiedades específicas de la función
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Class-specific function properties
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Funciones especiales miembro
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Special member functions
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Plantillas
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Templates
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Varios
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Miscellaneous
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Montaje en línea
 
Ejecuta de forma condicional código .
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Conditionally executes code.
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Se utiliza cuando el código debe ser ejecutada sólo si una condición está presente .
Original:
Used where code needs to be executed only if some condition is present.
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Contenido

[editar] Sintaxis

if ( expression ) statement_true
if ( expression ) statement_true else statement_false

[editar] Explicación

expression deberá ser una expresión, convertible a bool .
Original:
expression shall be an expression, convertible to bool.
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Si se evalúa como true, se pasa el control a statement_true, statement_false (si está presente) no se ejecuta .
Original:
If it evaluates to true, control is passed to statement_true, statement_false (if present) is not executed.
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De lo contrario, el control pasa a statement_false, statement_true no se ejecuta .
Original:
Otherwise, control is passed to statement_false, statement_true is not executed.
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[editar] Palabras clave

if, else

[editar] Ejemplo

El siguiente ejemplo muestra varios casos de uso de la declaración if
Original:
The following example demonstrates several usage cases of the if statement
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#include <iostream>
 
int main()
{
    int i = 2;
    if (i > 2) {
        std::cout << "first is true" << '\n';
    } else {
        std::cout << "first is false" << '\n';
    }
 
    i = 3;
    if (i == 3) std::cout << "i == 3" << '\n';
 
    if (i != 3) std::cout << "i != 3" << '\n';
    else        std::cout << "i != 3 is false" << '\n';
}

Output:

first is false
i == 3
i != 3 is false