Namespace
Varianti

Istruzione if

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General topics
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Controllo del flusso
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Flow control
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Dichiarazioni esecuzione condizionale
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Conditional execution statements
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if statement
Iterazione dichiarazioni
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Vai dichiarazioni
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Jump statements
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Funzioni
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Functions
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dichiarazione di funzione
lambda funzione dichiarazione
funzione di modello
specificatore inline
eccezioni specifiche (deprecato)
noexcept specificatore (C++11)
Eccezioni
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Exceptions
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Tipi
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Types
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decltype specifier (C++11)
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cv specificatori
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Inizializzazione
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Letterali
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rappresentazioni alternative
Utilities
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Utilities
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Tipi
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Types
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Lancia
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conversioni implicite
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Classi
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Classes
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Specifiche per una classe di funzioni proprietà
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esplicito (C++11)
statico
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Modelli
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classe template
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Varie
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Miscellaneous
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Montaggio in linea
 

Esegue in modo condizionale il codice.

Usato dove il codice deve essere eseguito solo se una certa condizione è presente.

Indice

[modifica] Sintassi

if ( espressione ) istruzione_vero
if ( espressione ) istruzione_vero else istruzione_falso

[modifica] Spiegazione

espressione deve essere un'espressione, trasformabile in bool.

Se restituisce true, il controllo viene passato a istruzione_vero, istruzione_falso (se presente) non viene eseguita.

In caso contrario, il controllo viene passato a istruzione_falso, istruzione_vero non viene eseguita.

[modifica] Parole chiave

if, else

[modifica] Esempio

L'esempio seguente mostra diversi casi di utilizzo dell'istruzione if 

#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
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/language/if&oldid=25953"