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From: postmast.root.admi.gov@iname.com (blargg)
Subject: Re: Suggestion: "typeof" keyword
Date: 1999/08/24
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In article <37C1B67F.B5B0B51A@cds.duke.edu>, Max TenEyck Woodbury
<mtew@cds.duke.edu> wrote:

> 'const' and 'volatile' are distinct attributes from the basic type
> of a data item. If they appear at the top level, they should be
> removed. After all, the main purpose of 'typeof' is to allow
> correctly typed copies to be instanced. One of the reasons for 
> making the copy of something is to manipulate it in some way while 
> leaving the original unchanged. Preserving 'const' at the top level
> could prevent this.
> 
> In the one bad example given, some trouble was taken to throw away
> 'const' at a lower level.
> 
> The original was
> 
> > any_type foo;
> > typeof(foo)* bar = &foo;
> >
> > And now assume any_type is int const.
> 
> The correct way to do this would be:
> 
> any_type foo;
> typeof(&foo) bar = &foo;
> 
> With any_type as int const, bar's type is * int const.

And one could remove the pointer and get a real const int from that:

    template<typename T>
    struct derefed_type;

    template<typename T>
    struct derefed_type<T*> {
        typedef T type;
    };

    typename derefed_type<typeof (&foo)>::type bar = foo; // bar->const int

I'm still for object allowed on LHS of scope resolution operator :: that
typeof () could be implemented on top of by the user.


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