From maintainers-request at octave dot org Thu Dec  8 22:39:28 2005
Subject: Re: message ids for warnings and errors
From: Paul Kienzle <pkienzle at users dot sourceforge dot net>
To: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
Cc: octave maintainers mailing list <maintainers at octave dot org>
Date: Thu, 8 Dec 2005 23:38:09 -0500


On Dec 7, 2005, at 8:41 PM, John W. Eaton wrote:

> | Similarly, octave-forge has 27 instances, including
> |
> |    warn_divide_by_zero = 0;
> |    warn_divide_by_zero = wdz;
> |
> | Maybe warn could have another state 'expected' which
> | suppresses the warning in the local scope?
>
> I think I'd rather avoid the extra complexity.  But maybe you see a
> simple way to imlement it?

The obvious way is to maintain a list of warning
names and states for the current function context
and run through this list when the function returns.
This does mean the majority of functions have to
pay for a feature they do not use, so not an ideal
solution.

A generalization of this is to support an
on_return("...") eval-like statement which
is called just before the function returns.
This is handy for implementing post-condition
checks for programming by contract, but not
otherwise very useful.

An ugly alternative is to hook into the symbol
table with a new octave type which is a subclass
of the structure type.  When a warning state is
set, add a field to the __expected_warning__
structure mapping warning name with the old state.
At the end of the function, when the current
symbol table is deleted and __expected_warning__
is freed, all warning states can be restored.

Either way, this seems like a low priority
issue.

- Paul