Re: add a way to declare global variables

[Bernd Eggink]

Am 12.12.2009 21:41, schrieb Chet Ramey:
> On 12/12/09 5:28 AM, Bernd Eggink wrote:
> > Am 10.12.2009 10:40, schrieb konsolebox:
> >
> > > I hope the development team will also consider adding a way in bash to
> > > declare global variables inside a function perhaps either with an
> > > option in typeset or declare like -g (same as zsh) and/or a builtin
> > > function like global as similar to local.
> >
> > I second that. I'm missing this feature badly. Presently, you can only
> > get around this restriction by using a lot of ugly and dangerous 'eval's.
>
> OK.  I'm interested in use cases for this feature.  What are you trying
> to do that you're missing it "badly?"

One example is introducing some kind of data encapsulation in bash, or 
even a modest form of object orientation. You may laugh at it, but I 
think it might be useful in complex scripts. I experimented a little and 
came up with 'classes' consisting of a function, and 'objects' 
consisting of a function (representing the interface) plus an equally 
named associative array (containing the data). The difficulties arise if 
you want to create an object 'a' of class X by saying

   X create a

You can declare a function 'a' dynamically within function X (using 
eval), but you can't declare a (global) associative array 'a' there. So 
that's where a global declaration would be desirable. The alternative is 
to print the declarations and eval the whole thing in the current 
environment, but that is very inconvenient and can cause nasty quoting 
problems.

Regards,
Bernd

--
Bernd Eggink
http://sudrala.de