Proposal: Extensible exceptions

[Henning Thielemann]

On Fri, 18 Jul 2008, Brandon S. Allbery KF8NH wrote:

> On 2008 Jul 18, at 11:05, Ian Lynagh wrote:
>
>> On Thu, Jul 17, 2008 at 09:16:36AM -0400, Isaac Dupree wrote:
>>> 
>>> I'm not entirely happy with this particular sketch of a proposal, but do
>>> people think that my initial issue is something to be concerned about at
>>> all?  (I'd be glad to be disproved :-)
>> 
>> It's hard to say if it'll be a problem in practice - we don't have any
>> experience with writing exception hierarchies.
>
> I'm going to ask a possibly silly question:  has anyone thought about this 
> vis-a-vis Simon's proposal of a new signals API?  It's not that unusual for 
> signals (usually SIGUSR1/SIGUSR2, often SIGINT, SIGHUP, sometimes SIGABRT, 
> SIGQUIT) to be used as asynchronous triggers --- which might be best 
> represented in the "Haskell world" as special exceptions.  Likewise, it often 
> makes sense to treat SIGPIPE, SIGHUP, SIGINT as exceptions instead of 
> signals.

I have seen this solution in Modula-3 (like exception ThreadAlerted), but 
I'm not happy with it, since the occurence of a signal is not specific to 
the IO action you call (like CouldNotOpenFile to 'open'). I would use a 
separate mechanism for signal handling.