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In article 1e7a@mule1.mindspring.com, abell@mindspring.com (Andrew Bell) writes:

>2) From a previous post on this group, it looks like the standard will
>allow one to define conversion operators for pre-existing, source code
>untouchable data types.  Yes? No? What will this look like? I have the
>May copy of the WP, and don't see any mention of this.

I'm not sure I understand what you are asking. If you mean can you define
a conversion operator from a user-defined class to a predefined type
like int or double, then yes, that has long been part of C++.
	class myclass {
	public:
		operator int() { ... }
	};

>3) I often write what I call "pure wrapper" classes to give access
>protection and data abstraction to pre-existing data types.  A pure
>wrapper class is a class that adds no member variables or virtual
>member functions to a class/struct that has no virtual functions of
>its own, so their size and alignment should be the same and casting
>between the two should be perfectly safe.  The new standard doesn't
>have any special support (for example, allowing it automatically) for
>this, does it?

I assume you mean a class like
	class Short { short val; };
with non-virtual member functions added. You can't assume the size and
alignment of the class will be the same as its only data member, and no,
the standard provides no special support for this special case.

Example: It is common for shorts to be aligned on 2-byte boundaries,
but all structured types to require alignment on 4-byte boundaries.
In this case, all struct types would have a size which is a
multiple of 4.  Casting between short* and Short*, or between
short& and Short&, could cause problems.

>4) With RTTI, a derived class that doesn't change any virtual member
>funcs or add any properties to a base class still evaluates to a
>different object type, correct?

Yes. The typeids of two types compare equal if and only if they are
the same type. Base and derived classes are not ever the same type.

---
Steve Clamage, stephen.clamage@eng.sun.com




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