I'm iworking on a patch for Perl 5 that implements the Perl 6 closure
traits (ENTER/LEAVE/...) as special blocks. There are several details
that aren't clear to me from either S04 or the spec tests; I apologize
if these have been discussed before, as I haven't been following p6l.
I'm also not subscribed, so if people could keep me in the CC that would
be appreciated.
- Presumably when an exception is thrown through a block, the LEAVE and
POST queues are called (in that order). What if a PRE block fails: is
the POST queue on the same block called? (Do you have to satisfy your
post-conditions even if your pre-conditions failed?)
- If a POST block is called as a result of a thrown exception, and it
fails, which exception 'wins'?
- Presumably if an ENTER block dies, the rest of that ENTER queue is
abandoned. Does that also apply to the LEAVE queue? What should
{
LEAVE { say "leave1" }
LEAVE { say "leave2"; die "foo"; }
}
print? Similarly POST: once one post-condition has failed, are
subsequent post-conditions checked?
- Can a try block catch an exception thrown from its own ENTER or LEAVE
queue? For example in this case:
try {
try {
ENTER { die "foo" }
CATCH { default { say "caught inside" } }
}
CATCH { default { say "caught outside" } }
}
which CATCH block gets the exception? What about PRE/POST: can you
CATCH failure of your own pre-/post-conditions?
- Does it make any difference in any of the above if 'die' is replaced
by 'exit'?
Ben
