C + + Operators

1, conversion operators: A special class member function. When the operator is defined, the compiler will call it automatically where the built-in transformations can be used :

classsmallint{ Public: SmallInt (inti =0): M_val (i) {if(I <0|| i >255)            ThrowStd::out_of_range ("Bad SmallInt initializer"); }    //The conversion function must be a member function, usually defined as a const    operator int()Const{returnM_val;}Private: std::size_t m_val;};intMain () {SmallInt Si ( A); DoubleDval =4.5; //si converted to int, then converted to double    if(Si >=dval) {}    //si converted to int, then converted to bool    if(SI) {} cout<< si << Endl;//si converted to int//3.541 is converted to int first, and then the smallint object is constructed with intSmallInt Si2 =3.541; intIval = static_cast<int> (SI2) +3;//an explicit conversion    return 0;}

In addition, the language allows only one-time (Automatic) class-type conversions . That is, (only) through the conversion operator, if the C type can be converted to type B, the B type can be converted to type A, then the C type cannot be converted directly to type A.

Resources:

"C + + Primer"

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C + + Operators