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All the Perl that's Practical to Extract and Report

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  • If you have
    my $f1 = Foo->new( 1, 2 );
    my $f2 = Foo->new( 1, 2 );
    you cannot say whether or not they are identical, because you do not know what else the constructor might have done. For instance, it might have recorded a timestamp, connected to a different database, or something else that is not necessarily the same from call to call.

    However, if you have
    my $f1 = Foo->new( 1, 2 );
    my $f2 = $f1;
    then the object are the same because they are pointing at the same data. Indeed, their string values should be the same (although the class may have overloaded the stringify method to introduce some sort of randomness).

    Comparing the stringified versions of objects can be useful. For instance, you can take a list of references and pull out the unique objects so you only call a method once on each object.

    However, none of this probably means anything to your module :)
    • Oh, I realize that $f1 and $f2 could be different. I was making the assumption (because I was too lazy to write out the code) that there wasn't anything tricky going on behind the scenes.

      Actually, another thing you can do is use and define your own "==" operator. Consider:

      package Foo;
      use strict;
      use overload "==" => \=

      sub new{
          my($class, $arg1, $arg2) = @_;
              _arg1 => $arg1,
              _arg2 => $ar

      • Whoops - didn't mean to hit submit yet. I was going to say that, even defining "==" doesn't help with my module and this is one case where Perl's OO begins to show its clunkiness, because now you have to deal with different types (strings and numbers vs references). I'm not saying it's impossible - I'm just saying it's extremely difficult, and you're better off subclassing.