Question

Suppose, if a conversion from one type another type is not available through explicit casts e.g static_cast, Would it be possible to define explicit conversion operators for it?

Edit:

I’m looking for a way to define explicit conversion operators for the following:

class SmallInt {

public:

    // The Default Constructor
    SmallInt(int i = 0): val(i) {
        if (i < 0 || i > 255)
        throw std::out_of_range("Bad SmallInt initializer");
    }

    // Conversion Operator
    operator int() const {
        return val;
    }

private:
    std::size_t val;

};

int main()
{
     SmallInt si(100);

     int i = si; // here, I want an explicit conversion.
}

Answer 1

For user defined types you can define a type cast operator. The syntax for the operator is

operator <return-type>()

You should also know that implicit type cast operators are generally frowned upon because they might allow the compiler too much leeway and cause unexpected behavior. Instead you should define to_someType() member functions in your class to perform the type conversion.

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Not sure about this, but I believe C++0x allows you to specify a type cast is explicit to prevent implicit type conversions.