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From: rfg@NCD.COM (Ron Guilmette)
Newsgroups: comp.lang.c++
Subject: Re: Smart pointers and Stupid people (my reactions and a new idea)
Message-ID: <3704@lupine.NCD.COM>
Date: 4 Feb 91 21:53:37 GMT
References: <3348@lupine.NCD.COM> <1991Jan19.190403.24325@clear.com>
Organization: Network Computing Devices, Inc., Mt. View, CA
Lines: 38

Regarding the idea of allowing dfeclarations of class T* { ... };

In article <1991Jan19.190403.24325@clear.com> rmartin@clear.com (Bob Martin) writes:
>>... however I fear that
>>Bjarne will never like it.  The reason?  Well, it makes the language
>>"mutable" (in Stroustrup's terms)...
...
>
>  But don't the unary operator& and operator*  already violate this
>  rule of mutability?  ARM 13.4 implies that there is no return
>  type restriction on these operators.  So by using an Y operator*(X*)
>  you "Change the meaning of unary * when applied to a pointer type value."

You are both right an wrong.

Note that those operators can only be defined for parameters
which have either some class type or some reference-to-class type.

Now in the case of operator*, you are dead wrong.  Allowing a definition
of this operator for some class type does not make the language mutable
because operator* has no existing "built-in" definition for objects of
a class type.  Thus, by providing your own explicit definition for
operator* for one of your own class types, you are not changing the
meaning of any previously existing operator which was legally applicable
to objects of that class type.

In the case of (unary) operator& however you make a very good point.  In
fact it seems to me that Stroustrup has in fact violated his own principal
of "non-mutability" when he allowed (unary) operator& to be defined by the
user for class types.

I will make it a point to raise this philosophical inconsistancy with x3j16.

-- 

// Ron Guilmette  -  C++ Entomologist
// Internet: rfg@ncd.com      uucp: ...uunet!lupine!rfg
// Motto:  If it sticks, force it.  If it breaks, it needed replacing anyway.