Yuval Kogman wrote:
>On Thu, Oct 06, 2005 at 14:27:30 -0600, Luke Palmer wrote:
>
>
>>On 10/6/05, Yuval Kogman <[EMAIL PROTECTED]> wrote:
>>
>>
>>> when i can't open a file and $! tells me why i couldn't open, i
>>> can resume with an alternative handle that is supposed to be the
>>> same
>>>
>>> when I can't reach a host I ask a user if they want to wait any
>>> longer
>>>
>>> when disk is full I ask the user if they want to write somewhere
>>> else
>>>
>>> when a file is unreadable i give the user the option to skip
>>>
>>>
>>I'm not bashing your idea, because I think it has uses. But I'll
>>point out that all of these can be easily accompilshed by writing a
>>wrapper for open(). That would be the usual way to abstract this kind
>>of thing.
>>
>>
>
>
>
Writing a "wrapper" may be the implementation mechanics:
sub safe_open()
{
call;
CATCH { when E::AccessDenied { return show_user_setuid_dialog(); }}
}
&open.wrap(safe_open);
But this is just one way to do it, and it fails to provide for "helping"
other people's code: Yuval's GUI environment would offer to fix the
problem for ALL file related calls (open, dup, popen, ad nauseum), and
would not have to worry about the order in which calls are wrapped. But
see below.
>Stylistically I would tend to disagree, actually. I think it's cleaner to use
>exception handling for this.
>
>Also, this implies that you know that the errors are generated by open. This
>is OK for open(), but if the errors are generated from a number of variants
>(MyApp::Timeout could come from anywhere in a moderately sized MyApp), then
>wrapping is not really an option.
>
>
I think that what your proposal *really* requires is uniformity. There
are other ways to get the same behavior, including an abstract factory
interface for exception construction (would provide "virtual
constructor" for exceptions, so permitting userspace to insert a 'retry'
behavior), but it has the same vulnerability: the p6core must cooperate
in uniformly using the same mechanism to report errors: throw, fail,
die, error, abend, whatever it's eventually called.
sub *::throw(...)
{
return recover_from_error([EMAIL PROTECTED])
or P6CORE::throw([EMAIL PROTECTED]);
}
=Austin
