Peter Scott wrote:
>
> I still think the explanation can be made simpler with fewer
> forward references. I'll have another try: [snip, but save]
>
> I note that under these rules it would be possible to have
> "try { ... } finally { }" with no catch blocks. I guess
> that's okay.
Have I got news for you. 88v2d1 not only allows that, it allows
try { } catch { } finally { } catch { }
it also allows
try { } finally { } finally { }
and this example of its use is given in the draft.
my ($p, $q);
try { $p = P->new; $q = Q->new; ... }
finally { $p and $p->Done; }
finally { $q and $q->Done; }
This construct makes sure that if $q is successfully
constructed, then $q->Done is invoked even if $p->Done
raises an exception.
Your explanation still assumes try followed by 0 or more
catch clauses, followed by 0 or 1 finally clause. The draft
does those cases just an you (and I) would want them to, but
it allows for try followed by 0 or more clauses each of which
is either a catch clause or a finally clause. This mechanism
has been shown to have at least the two uses shown above, it
has a well defined semantics, and it can be easily avoided.
Here's one thing we could do. We could define a very simple
set of rules for the common but restricted case of a try
followed by an optional catch, followed by an optional finally.
That covers most cases. Then, we could refer to the more
complete rules for the more complex cases.
Yours, &c, Tony Olekshy
