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「cpp/language/explicit」の版間の差分

提供: cppreference.com
< cpp‎ | language
細 (Use {{lc}}. Update links. Various fixes.)
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{{tr_note}}
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{{title|explicit }}
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{{title|explicit specifier}}
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{{cpp/language/navbar}}
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{{tr|コンストラクタと暗黙の型変換を許可していない{{mark since c++11}}変換演算子を指定します|Specifies constructors and {{mark since c++11}} conversion operators that don't allow implicit conversions}}
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===構文===
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{{sdsc begin}}
 
{{sdsc begin}}
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{{sdsc | {{c|explicit}} {{spar|class_name}} ( {{spar|params}} ) }}
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{{sdsc|
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{{sdsc  | {{c|explicit operator}} {{spar|type}} ( ) {{mark since c++11}} }}
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{{|explicit}}
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{{|{{}}
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{{|explicit }} {{spar|}} {{}}
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}}
 
{{sdsc end}}
 
{{sdsc end}}
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===例===
 
===例===
 
{{example|code=
 
{{example|code=
 
struct A
 
struct A
 
{
 
{
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     A ( int ) {}
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     A(int) { }
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     operator int() const { return 0; }
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     operator () const { return ; }
 
};
 
};
  
 
struct B
 
struct B
 
{
 
{
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     explicit B(int) {}
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     explicit B(int) { }
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     explicit operator int() const { return 0; }
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     explicit int
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() const { return ; }
 
};
 
};
  
 
int main()
 
int main()
 
{
 
{
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    // A is has no explicit ctor / conversion, everything is fine
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     A a1 = 1;
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     A a1 = 1;
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     A a2(2);
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     A a2 ( 2 );
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     A a3 {};
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     A a3 { 3 };
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     int
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     int na1 = a1;
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     int na2 = static_cast<int>( a1 );
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na1 = a1;
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    B b1 = 1; // Error: implicit conversion from int to B
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     na2 = static_cast<>(a1);
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     B b2 ( 2 ); // OK: explicit constructor call
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     B b3 { 3 }; // OK: explicit constructor call
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B b1 = 1; // :B
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    int nb1 = b2; // Error: implicit conversion from B to int
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     B b2(2); // :
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     int nb2 = static_cast<int>( b2 ); // OK: explicit cast
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     B b3 {}; // :
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int
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=
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b2; // :
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B
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     nb2 = static_cast<>(b2); //
 
}
 
}
 
}}
 
}}
  
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2018年10月3日 (水) 04:28時点における版

 
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