switch statement — cppreference.com
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Exécute le code en fonction de la valeur d'un argument intégrante
Original:
Executes code according to value of an integral argument
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Lorsqu'une ou plusieurs de nombreuses branches de code doivent être exécutées selon une valeur intégrale .
Original:
Used where one or several out of many branches of code need to be executed according to an integral value.
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Syntaxe
switch ( expression ) {
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Explication
expression doit être une expression, convertible en une valeur entière .
Original:
expression shall be an expression, convertible to an integer value.
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Tous les constant_expressions doit être des expressions constantes, convertibles en un nombre entier, ce qui est unique dans cette déclaration switch
Original:
All constant_expressions shall be constant expressions, convertible to an integer value, which is unique within this switch statement
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Si la expression prend une valeur égale à la valeur de l'une des constant_expressioni défini, le statementi (s'il est présent) et tous les états ultérieurs (sauf default_statement, si elle est présente) sont exécutées. Si la valeur de la expression ne correspond à aucune des constant_expressions, le default_statement est exécutée si présent .
Original:
If the expression evaluates to a value, equal to the value of one of the defined constant_expressioni, the statementi (if present) and all subsequent statements (except default_statement, if present) are executed. If the value of the expression does not match any of the constant_expressions, the default_statement is executed if present.
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Il est utile de noter que, si l'exécution des instructions suivantes est indésirable, l'
instruction break
Original:
break statement
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peuvent être utilisés. Dans ce cas, l'exécution de l'instruction se termine switch .
Original:
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Mots-clés
Exemple
Le code suivant illustre l'utilisation de plusieurs cas de l'interrupteur' déclaration
Original:
The following code shows several usage cases of the switch statement
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#include <iostream> int main() { int i = 2; switch (i) { case 1: std::cout << "1"; case 2: std::cout << "2"; //execution starts at this case label case 3: std::cout << "3"; case 4: case 5: std::cout << "45"; break; //execution of subsequent statements is terminated case 6: std::cout << "6"; } std::cout << '\n'; switch (i) { case 4: std::cout << "a"; default: std::cout << "d"; //there are no applicable constant_expressions //therefore default_statement is executed } std::cout << '\n'; switch (i) { case 4: std::cout << "a"; //nothing is executed } }
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