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From: maxtal@Physics.usyd.edu.au (John Max Skaller)
Subject: Re: Redundant Using Declarations
Date: 1995/05/21
Message-ID: <D8xsur.Ew2@ucc.su.OZ.AU>#1/1
X-Deja-AN: 103029336
sender: news@ucc.su.OZ.AU
references: <3pi75q$ihm@offas_dike.sbil.co.uk>
organization: School of Physics, University of Sydney, Australia
newsgroups: comp.std.c++

In article <3pi75q$ihm@offas_dike.sbil.co.uk>,
Marc Shepherd <shepherd@debussy.sbi.com> wrote:
>Subclause 7.3.3 of the draft WP says:
>
>   A using-declaration is a declaration and can therefore be
>   used repeatedly where (and only where) multiple declarations
>   are allowed.

	No: a definition is also a declaration, and it _cannot_
be repeated: it isn't a question of where "multiple declarations"
are allowed: multiple definitions in the one scope are never
allowed, and multiple declarations which are not definitions
always are. (Multiple declarations which are not definitions
must obey certain rules about not changing linkage attributes 
or type or return type)
>
>It further gives the following examples of this rule:
>
>   namespace A {
>      int i;
>   }
>
>   namespace A1 {
>      using A::i;
>      using A::i; // ok: double declaration
>   }
>
>   void f()
>   {
>      using A::i;
>      using A::i; // error: double declaration
>   }
>
>   class B {
>      int i;
>   };
>
>   class X : public B {
>      using B::i;
>      using B::i; // error: double member declaration
>   };
>
>My question is: in the definition of namespace A1 shown above, why
>is the redundant using declaration of A::i well-formed, considering
>that the following would not be:
>
>   namespace A1 {
>      int i;
>      int i;
>   }

	Because the declaration "int i" is a definition.

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        JOHN (MAX) SKALLER,         INTERNET:maxtal@suphys.physics.su.oz.au
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