From bug-octave-request at bevo dot che dot wisc dot edu Thu Mar 18 12:51:39 2004
Subject: Re: global /exist ?
From: Christoph Ellenberger <c dot ellenberger at gmx dot net>
To: paulthomas2 at wanadoo dot fr, bug-octave@bevo.che.wisc.edu
Date: Thu, 18 Mar 2004 19:36:50 +0100

Hi Paul T,
on the other hand one part of the program has to be the first to declare it=
=20
global and initialize, and so a construction like:

global xx
if (!exist("xx"))
  init xx;
endif

in a modular environment may make sense...

PS. I missed this discussion so there might be already some counter argumen=
t=20
about that.

BTW and you are right if you say one can also write something like:

global xx
if isempty(xx)
  init xx;
endif

but then xx is not allowed to be in an empty state.... =20
Sometimes one just has to make compromises :)
Christoph

On Thursday 18 March 2004 16:42, Paul THOMAS wrote:
> Hi Christoph,
>
> It seems to me that not only is this a compatability issue but a logical
> one as well.  There was a discussion some months ago about how global
> functions, although I do not recall on which list.  It seems to me that
> making a variable global must mean that it exists in the current scope,
> otherwise what would be the meaning to other scopes?  Thus, making global
> an implicit constructor of an empty matrix, if there is not already a
> global variable with that name, or a variable local to the current scope,
> is logically mandatory.
>
> Paul T
>
> > Message du 16/03/04 12:39
> > De : Christoph Ellenberger <c dot ellenberger at gmx dot net>
> > A : bug-octave at bevo dot che dot wisc dot edu
> > Copie =E0 :
> > Objet : global /exist ?
> >
> > Hi,
> > this just occured to me... using the latest 2.1.57. I dunno if it is a
> > bug or intended.
> >
> > octave:1> exist("hh")
> > ans =3D 0
> > octave:2> global hh
> > octave:3> exist("hh")
> > ans =3D 1
> >
> > even if hh is not existing as a global variable...
> > further hh is now initialised as a matrix.
> > octave:4> hh
> > hh =3D [](0x0)
> >
> > AFAIK this breaks the behaviour of precedent versions at least (2.1.50).
> >
> > Greetings
> > Christoph
> >
> >
> >
> > -------------------------------------------------------------
> > Octave is freely available under the terms of the GNU GPL.
> >
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=2D-=20
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 ...
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (o =
o)
=2D----------------------oOO--(_)--OOo--------------------------

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 present coordinates:

Christoph Ellenberger
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0Solid State Physics Laboratory HPF E9
Schaffhauserstrasse 443 =A0 =A0 =A0 ETH Hoenggerberg
CH-8050 Zuerich =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 CH-8093 Zuerich

Tel ++41 (0)43 299 92 72 =A0 =A0 =A0 =A0(0)1 633 23 13

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Email =A0 C dot Ellenberger at gmx dot net

=2D---------------------------------------------------------------------



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