[792] in Coldmud discussion meeting

Re: exception handling...

daemon@ATHENA.MIT.EDU (Thu Aug 31 18:07:12 1995 )

Date: Thu, 31 Aug 1995 17:53:09 -0400 (EDT)
From: James C Deikun <jcdst10+@pitt.edu>
To: 869683 Gillespie Brandon James <brandon@smithfield.declab.usu.edu>
Cc: coldstuff@MIT.EDU
In-Reply-To: <9508310725.AA04032@smithfield.declab.usu.edu>



On Thu, 31 Aug 1995, 869683 Gillespie Brandon James wrote:

> I'm mulling over the reconstruction of exception handling (catch) to be
> slightly different.  The best way to explain this is with an example:
> 
> for obj in (list) {
>     catch {
>         obj.query_test();
>     } handle ~locked {
>         sender().print("Object is locked.");
>     } handle others {
>         sender().print("Error: " + toliteral(error) + " encountered!");
>     } otherwise {
>         sender().print("Test is sucessful for: " + obj.name());
>         valid = valid + [obj];
>     }
> }

This isn't an exception handler, it's a switch statement.

> Basically, each handle ~error line is for whichever error, where the
> handle others is for all others.  If it does not exist, the error
> is propogated normally.

If you get an unexpected error, why not print a traceback or something, 
anyway?  It'd be better to spend effort on making a non-cryptic format 
for them for nonprogrammers.

If you think it's needed for cleanups, you could be onto something 
though.  However, is this the best way to implement it?  'finally' is a 
very clean and simple thing, for all its disadvantages (like not 
inherently knowing if the code inside worked).

> The otherwise clause we are still hung up on, but Jeff Bellegarde and
> I feel it is better than:
> 
> for obj in (list) {
>     catch {
>         obj.query_test();
>         sender().print("Test is sucessful for: " + obj.name());
>         valid = valid + [obj];
>     } handle ~locked {
>         sender().print("Object is locked.");
>     } handle others {
>         sender().print("Error: " + toliteral(error) + " encountered!");
>     }
> }

Better only as a switch statement.  If you want a switch statement, why 
not use one?

--
James "brainwashed convert of LISP folks" Deikun