Playing around with different MROs to try and figure out general purpose algorithms for detecting 'unreachable' methods. That's when I got confused by Class::C3. Imagine the following hierarchy. If every one of those classes has a 'target' method, I expect, with C3, that the calling order would be "One", "Two", "Three", "Four", "Six" and "Five".
5Here's my code:
#!/usr/bin/perl -l
use strict;
use warnings;
package One;
our @ISA = qw/Two Three/;
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package Two;
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package Three;
our @ISA = qw/Four Six/;
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package Four;
our @ISA = 'Five';
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package Five;
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package Six;
use Class::C3;
sub target { print __PACKAGE__; shift->next::method }
package main;
Class::C3::initialize();
One->target;
This prints out:
One Two Three Four Five Six
Because 'Three' inherits from 'Four' and 'Six', I'm expecting 'Six' to get called before 'Five' (which 'Four' inherits from). What did I miss?
Note: the rationale behind this was simple. Let's say that only 'Two' and 'Six' define a 'target' method (the graphic I created to understand this). With Perl's default MRO, '&Six::target' is unreachable. I wasn't sure if that was the case with Class::C3. That's why I'm a bit confused.
Hi,
According to Class::C3 docs, the C3 algorithm only guarantees that no class Parent will be called before Child.
In your case, when he gets to '4', he can call '5' because '6' is not a subclass of '5'.
If you add Five to the @Six::ISA, then you would see the behavior that you are expecting.
Best regards,
Re:Correct behavior
Ovid on 2009-01-31T18:49:18
Ah, OK. Thanks!
