exception types & objects

Stewart Gordon smjg_1998 at yahoo.com
Thu Oct 21 08:54:04 PDT 2010

On 19/10/2010 23:23, Jonathan M Davis wrote:
> Perhaps, but there is no real benefit in throwing anything other than
> an Exception (or Error upon occasion) and if we allow you to throw
> anything than catch(Exception e) won't catch them all. It also would
> pretty much violate nothrow since nothrow guarantees that no
> Exceptions are thrown from that function, and if you can throw any
> old object anyway...

Indeed, "Nothrow functions do not throw any exceptions derived from 
class Exception" - seems odd to me.

I think I've had two uses in my time for throwing something that isn't 
an Exception:
- in a previous version of SDWF, to handle an awkward corner case in the 
Windows dialog API, though I later found a better way of dealing with it
- in the runtime for an Unlambda to D compiler, to serve as the 
continuation object, though that could just as well be changed

I hadn't realised until now that D2 had changed to have a Throwable 
class and Error and Exception classes derived therefrom.  It seems the 
intention was to prevent a nothrow function throwing anything other than 
an Error, but it wasn't quite said right.  So any solution should 
probably prevent circumvention by creating a whole new subclass of 
Throwable.  (By a quick look through the Java API docs, checked 
exception classes are defined as Throwable minus the RuntimeException 
and Error subclasses.)


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