HP aC++/HP C A.06.20 Programmer's Guide

{
// Define Base2 function.
}
class Derived : public virtual Base1, public virtual Base2 {
// additional class details omitted
};
void main()
{
Base1 *bp1;
Base2 *bp2;
Derived *dp;
bp1 = new Derived;
bp2 = new Derived;
// dp = (Derived *) bp1;
// Problem: compile time error
// Can’t cast from virtual base.
// dp = (Derived *) bp2;
// Problem: compile time error
// Can’t cast from virtual base.
// dp = dynamic_cast<Derived *> bp1;
// Problem: compile time error
// Can’t cast from
// non-polymorphic type.
dp = dynamic_cast<Derived *> bp2; // OK
}
explicit Keyword
explicit Keyword
The explicit keyword is used for declaring constructor functions within class
declarations. When these functions are declared explicit, they cannot be used for implicit
conversions.
Usage
While constructors taking one argument are often useful in the design of a class, they
can allow inadvertent conversion in expressions. This can introduce subtle bugs. The
explicit keyword allows a class designer to prohibit such implicit conversions. It is
often used in the production of class libraries.
HP aC++ Keywords 181