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switch statement

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一般的なトピック
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General topics
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フロー制御
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Flow control
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条件付き実行文
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Conditional execution statements
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switch statement
繰り返し文
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Iteration statements
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文をジャンプします
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Jump statements
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機能します
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Functions
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関数の宣言
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関数テンプレート
の歴史。インライン指定
例外仕様 (廃止予定)
noexcept指定子 (C++11)
例外
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Exceptions
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名前空間
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Namespaces
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タイプ
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Types
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decltype specifier (C++11)
指定子
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Specifiers
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CV指定
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constexprの指定子 (C++11)
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初期化
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Initialization
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リテラル
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Literals
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Expressions
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代替表現
ユーティリティ
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Utilities
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タイプ
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Types
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型の別名宣言 (C++11)
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キャストします
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Casts
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暗黙の型変換
const_cast conversion
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Memory allocation
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クラス
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Classes
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クラス固有の機能特性
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Class-specific function properties
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明示 (C++11)
静的
特殊なメンバ関数
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Special member functions
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テンプレート
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Templates
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クラステンプレート
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その他
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Miscellaneous
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インラインアセンブリ
 
一体型の引数の値に応じてコードを実行します
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Executes code according to value of an integral argument
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どこで使用されるコードの多くの枝の1つまたはいくつかのうち、積分値に応​​じて実行する必要が.
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Used where one or several out of many branches of code need to be executed according to an integral value.
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目次

[編集] 構文

switch ( expression ) {
case constant_expression1 :
statement1 (オプション)
case constant_expression2 :
statement2 (オプション)
... ... ...
case constant_expressionn :
statementn (オプション)
default: default_statement (オプション)

}

[編集] 説明

expressionは、整数値に変換式でなければならない.
Original:
expression shall be an expression, convertible to an integer value.
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すべてconstant_expressionsは、このswitch文内で一意となる整数値に変換定数式でなければならない
Original:
All constant_expressions shall be constant expressions, convertible to an integer value, which is unique within this switch statement
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expressionが定義constant_expressioniのいずれかの値に等しい値に評価される場合は、statementi(存在する場合)およびそれ以降のすべてのステートメント(default_statement除いて、存在する場合)が実行されます。 expressionの値がconstant_expressionsのいずれとも一致しない場合は、存在する場合、default_statementが実行されます.
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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が使用可能であることを、覚えておくと便利です。その場合switch文の実行は終了します.
Original:
It is useful to note, that if the execution of subsequent statements is undesirable, the
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[編集] キーワード

switch, case, default

[編集]

次のコードは、スイッチ'文のいくつかの使用例を示しています
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:

2345
d