Hiding class pointers -- was it a good idea?

[eao197]

On Thu, 16 Aug 2007 01:35:17 +0400, Walter Bright  
<newshound1 at digitalmars.com> wrote:

> Bill Baxter wrote:
>> I'm starting to seriously wonder if it was a good idea to hide the  
>> pointers to classes.  It seemed kinda neat when I was first using D  
>> that I could avoid typing *s all the time.  But as time wears on it's  
>> starting to seem more like a liability.
>
> Having classes be by reference only has some serious advantages:
>
> 1) Classes are polymorphic and inheritable. By making them reference  
> only, the "slicing" problem inherent in C++ is completely and cleanly  
> avoided.

 From my expirience this is a problem of C++ beginners.

> 2) You can't write a class in C++ without paying attention to assignment  
> overloading and copy constructors. With classes as a reference type,  
> these issues are simply irrelevant.
>
> 3) Value types just don't work for polymorphic behavior. They must be by  
> reference. There's no way in C++ to ensure that your class instances are  
> used properly by reference only (hence (2)). In fact, in C++, it's  
> *extra work* to use them properly.

But from another side all types in C++ (internal or user defined) is a  
first class citizens. It is especially important in generic programming,  
where I can write:

template< class T >
class ValueHolder {
   T * m_value
public :
   ValueHolder() : m_value( new T() ) {}
   ...
};

and this code will work as with int, as with std::string, as with  
ValueHolder<SomeAnotherType>.

> Value types are fundamentally different from reference types. D gives  
> you the choice.

After some languages where there aren't distinction beetwen various kind  
of types (e.g. C++/Eiffel/Ruby) D looks very strange here. And this is one  
of the troubles in studying D.

-- 
Regards,
Yauheni Akhotnikau