Francis Glassborow wrote:
>In article <39D8DA5D.BD22D873@jps.net>, Dennis Yelle <dennis51@jps.net>
>writes
> >> Largely a matter of history. Actually if you look at it carefully you
> >> will find that this isn't really a pointer.
> >
> >OK. I give up.  In what sense is "this" not a pointer?
>
>In the sense that it is more akin to a reference in semantics, though it
>has the syntax of a pointer.

Meaning, I think, that 'this' is never legally NULL.

Also 'this' is not an lvalue so '&this', is ill-formed and a 'T*&r = this;'
can't bind 'r' directly to 'this'.

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.research.att.com/~austern/csc/faq.html                ]
[ Note that the FAQ URL has changed!  Please update your bookmarks.     ]

Niels Dekker <ndekker@REMOVETHISnki.nl> wrote:
>> Why hasn't C++ defined "this" to be a reference, instead of a
>> pointer?

Jim Hyslop wrote:
> I believe the D&E explains this. As I understand it, Stroustrup hadn't
> yet come up with references when he invented 'this'. By the time he
> invented references, changing the type of 'this' would be quite
> difficult.

I asked the same question in this NG several months ago, and got
essentially the same answer: history.

Of course, if you really want to, you can simulate a "this reference"
entity with (gasp!) a little preprocessor magic:

    #define self  (*this)

--
David R. Tribble, mailto:david@tribble.com, http://david.tribble.com

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.research.att.com/~austern/csc/faq.html                ]
[ Note that the FAQ URL has changed!  Please update your bookmarks.     ]

Francis Glassborow wrote:
>
> In article <39D7501C.D5BEE0DC@REMOVETHISnki.nl>, Niels Dekker
> <ndekker@REMOVETHISnki.nl> writes
> >Why hasn't C++ defined "this" to be a reference, instead of a pointer?
> >
> Largely a matter of history. Actually if you look at it carefully you
> will find that this isn't really a pointer.

OK. I give up.  In what sense is "this" not a pointer?

Dennis Yelle
--
I am a computer programmer and I am looking for a job.
There is a link to my resume here:
http://table.jps.net/~vert/

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html              ]

In article <39D8DA5D.BD22D873@jps.net>, Dennis Yelle <dennis51@jps.net>
writes
>> Largely a matter of history. Actually if you look at it carefully you
>> will find that this isn't really a pointer.
>
>OK. I give up.  In what sense is "this" not a pointer?

In the sense that it is more akin to a reference in semantics, though it
has the syntax of a pointer.

Francis Glassborow      Association of C & C++ Users
64 Southfield Rd
Oxford OX4 1PA          +44(0)1865 246490
All opinions are mine and do not represent those of any organisation

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html              ]

"Francis Glassborow" <francis.glassborow@ntlworld.com> wrote in message
news:PMbW$VAyTf25Ew9V@ntlworld.com...
> In article <39D8DA5D.BD22D873@jps.net>, Dennis Yelle <dennis51@jps.net>
> writes
> >> Largely a matter of history. Actually if you look at it carefully you
> >> will find that this isn't really a pointer.
> >
> >OK. I give up.  In what sense is "this" not a pointer?
>
> In the sense that it is more akin to a reference in semantics, though it
> has the syntax of a pointer.
>

Example: The behaviour of the program is undefined, if -this- does not point
to an object of -this-type, similar to a reference, but unlike pointers
which may point to NULL.

Marco


---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.research.att.com/~austern/csc/faq.html                ]
[ Note that the FAQ URL has changed!  Please update your bookmarks.     ]

On Tue,  3 Oct 2000 15:33:49 GMT, Francis Glassborow
<francis.glassborow@ntlworld.com> wrote:

} In article <39D8DA5D.BD22D873@jps.net>, Dennis Yelle <dennis51@jps.net>
} writes
} >> Largely a matter of history. Actually if you look at it carefully you
} >> will find that this isn't really a pointer.
} >
} >OK. I give up.  In what sense is "this" not a pointer?
}
} In the sense that it is more akin to a reference in semantics, though it
} has the syntax of a pointer.

As far as I remember, 'this' was in C++ before references were part of the
language.  After that, there was too much existing code to change the
behaviour.


Have fun,
Alex.

--
My email address is intentionally mangled to foil spambots.
Please remove the "---filter---" from the address for replying.
Sorry for the inconvenience.

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.research.att.com/~austern/csc/faq.html                ]
[ Note that the FAQ URL has changed!  Please update your bookmarks.     ]

Why hasn't C++ defined "this" to be a reference, instead of a pointer?

I'm just curious...

  Thanks in advance,

    Niels Dekker
    ndekker "at" nki "dot" nl

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html              ]

In article <39D7501C.D5BEE0DC@REMOVETHISnki.nl>,
  Niels Dekker <ndekker@REMOVETHISnki.nl> wrote:
> Why hasn't C++ defined "this" to be a reference, instead of a pointer?
I believe the D&E explains this. As I understand it, Stroustrup hadn't
yet come up with references when he invented 'this'. By the time he
invented references, changing the type of 'this' would be quite
difficult.

--
Jim
This message was posted using plain text only.  Any hyperlinks you may
see were added by other parties without my permission.
I do not endorse any products or services that may be hyperlinked to
this message.


Sent via Deja.com http://www.deja.com/
Before you buy.

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html              ]

In article <39D7501C.D5BEE0DC@REMOVETHISnki.nl>, Niels Dekker
<ndekker@REMOVETHISnki.nl> writes
>Why hasn't C++ defined "this" to be a reference, instead of a pointer?
>
Largely a matter of history. Actually if you look at it carefully you
will find that this isn't really a pointer.


Francis Glassborow      Association of C & C++ Users
64 Southfield Rd
Oxford OX4 1PA          +44(0)1865 246490
All opinions are mine and do not represent those of any organisation

---
[ comp.std.c++ is moderated.  To submit articles, try just posting with ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html              ]