switch statement – cppreference.com
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Führt Code nach Wert eines ganzzahligen Argument
Original:
Executes code according to value of an integral argument
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Dort eingesetzt, wo eine oder mehrere aus vielen Zweigen der Code nach einem ganzzahligen Wert ausgeführt werden müssen .
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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Syntax
switch ( expression ) {
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Erklärung
expression sind ein Ausdruck, umwandelbar in einen Integer-Wert sein .
Original:
expression shall be an expression, convertible to an integer value.
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Alle constant_expressions sind konstante Ausdrücke, umwandelbar in einen Integer-Wert, die einzigartig in diesem switch Aussage sein
Original:
All constant_expressions shall be constant expressions, convertible to an integer value, which is unique within this switch statement
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Wenn die expression ergibt einen Wert, der gleich dem Wert eines der definierten constant_expressioni die statementi (falls vorhanden) und allen nachfolgenden Aussagen (außer default_statement, falls vorhanden) werden ausgeführt. Wenn der Wert des expression mit keinem der constant_expressions wird die default_statement ausgeführt falls vorhanden .
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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Es ist nützlich, zu beachten, dass, wenn die Ausführung der nachfolgenden Aussagen ist unerwünscht, die
break-Anweisung
Original:
break statement
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verwendet werden können. In diesem Fall wird die Ausführung des switch Anweisung beendet .
Original:
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Keywords
Beispiel
Der folgende Code zeigt einige Anwendungsfälle der Switch Aussage
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 } }
Output: