🚀 go-pugleaf

In article <MATT.95Sep16194450@Austern>, Haim Kreitman
<haim_kreitman@mail.stil.scitex.com> wrote:

>> typedef type1;         // what does it mean ???

>> [Moderator's note: the STL documentation has some "code" that isn't
>> code.  This sort of line isn't supposed to be legal C++, it's just 
>> supposed to indicate that type1 is a typedef for something.  mha]

Haim and me once thought that this is a forward declaration for a type.
While reading the draft, I've noticed that there is a new keyword,
"typename", that is used for that purpose.

I think that STL should be updated to contain the "typename" keyword to
prevent confusion.

Etay.

-- Etay Bogner,
-- Etay_Bogner@mail.stil.scitex.com,
-- Scitex Corp.
-- Israel.
---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]

In article <Etay_Bogner-1709951504510001@metay_pc.stil.scitex.com>, Etay_Bogner@mail.stil.scitex.com (Etay Bogner) writes:
|> In article <MATT.95Sep16194450@Austern>, Haim Kreitman
|> <haim_kreitman@mail.stil.scitex.com> wrote:
|> 
|> >> typedef type1;         // what does it mean ???
|> 
|> >> [Moderator's note: the STL documentation has some "code" that isn't
|> >> code.  This sort of line isn't supposed to be legal C++, it's just 
|> >> supposed to indicate that type1 is a typedef for something.  mha]
|> 
|> Haim and me once thought that this is a forward declaration for a type.
|> While reading the draft, I've noticed that there is a new keyword,
|> "typename", that is used for that purpose.
|> 
|> I think that STL should be updated to contain the "typename" keyword to
|> prevent confusion.

My understanding is that the typename keyword may only be used in templates
to identify subtypes of the template parameters, which otherwise can not be
identified as a type.

for example:

template <T>
class foo {

  typename T::i;
  int var;

  void fn() {
    T::i *var;  //without the typename keyword this could either be a declaration
                //or an expression.
  }
};

The typename keyword has been added since the September 1994 draft but I'm not
sure exactly when.

-- 
Craig P. Forbes                      McCabe & Associates
                                     5501 Twin Knolls Road, Suite 111
craig@mccabe.com                     Columbia, MD 21045

---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]

craig@mccabe.com (Craig P. Forbes) writes:
	...
>My understanding is that the typename keyword may only be used in templates
>to identify subtypes of the template parameters, which otherwise can not be
>identified as a type.
	...
>template <T>
>class foo {
	
>  typename T::i;
>  int var;

>  void fn() {
>    T::i *var;  //without the typename keyword this could either be a declaration

<blink>?  What happened to minimalism...?  Couldn't this be just as
well have been coded...:

	typedef T::i dummynameoftype; // no syntax ambiguity here
	...
	dummynameoftype *var; // no ambiguity here either

Was a whole new keyword really introduced just for the purpose of
avoiding the template author the chore of thinking up a dummy type
name in this situation...?  Or am I missing something here...?


Alex
--
DISCLAIMER: these are TOTALLY personal opinions and viewpoints, NOT connected
in any way with my employer, nor any other organization or individual!
Email: martelli@cadlab.it                            Phone: +39 (51) 597313
CAD.LAB s.p.a., v. Ronzani 7/29, Casalecchio, Italia   Fax: +39 (51) 597120


---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]

>>>>> Craig P Forbes <craig@mccabe.com> writes:

> My understanding is that the typename keyword may only be used in templates
> to identify subtypes of the template parameters, which otherwise can not be
> identified as a type.

> for example:

> template <T>
> class foo {

>   typename T::i;

This line is semantically null, as the 'typename' keyword only affects the
immediate use of the scope expression, not subsequent uses.

>   int var;

>   void fn() {
>     T::i *var;  //without the typename keyword this could either be a declaration
>                 //or an expression.

This must be 'typename T::i *var;'.

>   }
> };

Jason

[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]