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Postings from July 2013
* David E. Wheeler <david@kineticode.com> [2013-07-25 12:45]:
> Could you do conditional checks for each catch that way, as Aristotle
> suggested? Would it be defined inside the parens, as in:
>
> my $retry = 0;
> while ( $retry < 5 ) {
> try { $some->transaction }
> catch my $err ( $err->isa('X::Transient') ) { ++$retry }
> }
>
> Seems a *little* weird, but not too bad. I guess global $_ would be
> the default just like for?
And then if you have multiple `catch`es, then what? catch my $err (this) {}
catch my $err (that) {} catch my $err (theother) {}?
You just name the variable over and over and over?
If you don’t want to, where does the name go? On the `try`?
try my $err { $some->transaction }
catch ( $err->isa('X::Transient') ) { ++$retry }
I mean that’s workable, but the scoping is utterly bizarre.
If you want to avoid the scope bizarreness you have two choices:
Either you put the `catch`es inside the `try`; then you need a form of
phasers and then you realise that generalises to other types and as you
start adding more of them you realise that all control flow can be seen
a special kinds of exceptions… and you have mutated into Perl 6. Which
is to say there is a reason Perl 6 went where it did and if you want to
do things really right, in many cases you will find yourself running
right after it.
Or else you use a global variable to avoid the need for declaration that
led you into the mess in the first place.
In cases like this I tend to prefer Perl 5 to stay Perl 5 rather than
trying to reinvent Perl 6 poorly within the constraints of Perl 5, since
if I want Perl 6 I know where I can** find it.
** For values of “can” equal “will eventually be able to”.
Regards,
--
Aristotle Pagaltzis // <http://plasmasturm.org/>
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