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Postings from July 2013
On Tue, Jul 23, 2013 at 2:04 PM, David Golden <xdg@xdg.me> wrote:
>
> that isa 'FOO'). However, if the exception needs to be parked in a
> global, I'd park it in $@ for consistency with what happens outside
> try/catch.
I nominate @@ for the stack of new exceptions, for consistency without
interference.
A "Yoda's exception system" (in which, drumroll please, there is no
try) can be effected
with a DEFER block.
C< catch FooE { ... } > might essentially expand into something like
OnScopeExit { # before, after, or during reassignment of locals?
my @CatchMe, @NewStack;
push @{ $_->isa('FooE') ? \@CatchMe : \@NewStack }, $_ for @@;
for ( @CatchMe ) {
...
};
@@ = @NewStack; # any advantage to *@ = \@NewStack ???
}
Why a stack, instead of just one variable? To handle situations where
deferred code throws another exception, as well as exceptions thrown
from DESTROY routines, thus
avoiding the problems caused clearing an unlocalized $@.
The big difference between $@ and the above-proposed @@ has to do with
clearing it: $@ gets cleared on all C<eval> calls; @@ would only get
items removed from it when they
are explicitly consumed, either by convention or by restricting access to it.
Further compatibility could be provided with
sub YodaTry(&) {
eval { shift ->() ; 1 } or push @@, $@
}
I see how one could create a pure-perl YodaCatch, using the hack from
Scope::local_OnExit, but the syntax would wind up looking like
local @YodaCatch = ( FooE => sub { ... }, );
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