Bug #42449 for Set-Scalar: Set::Scalar objects lose '=' overloading

Thu Jan 15 17:19:31 2009 jloverso [...] mathworks.com - Ticket created

Subject:

Set::Scalar objects lose '=' overloading

(This happens in Perl 5.8.8, and I've tested on MacOS 10.5.5, Linux, and Solaris). If two variables hold a reference to the same Set::Scalar object, then the '=' overload breaks. I suspect this might have something to do with the fact that the '+=' overload is inherited from Set::Scalar::Real. An example makes it clear: DB<1> use Set::Scalar DB<2> x $Set::Scalar::VERSION 0 1.22 DB<3> x $x = Set::Scalar->new(1..3) 0 Set::Scalar=HASH(0xcedb30) 'elements' => HASH(0xa5c960) 1 => 1 2 => 2 3 => 3 'universe' => Set::Scalar::Universe=HASH(0xc7b830) 'elements' => HASH(0xc87490) 1 => 1 2 => 2 3 => 3 'null' => Set::Scalar::Null=HASH(0xc7c200) 'universe' => Set::Scalar::Universe=HASH(0xc7b830) -> REUSED_ADDRESS 'universe' => undef DB<4> x $x += 4 0 Set::Scalar=HASH(0xcedb30) 'elements' => HASH(0xa5c960) 1 => 1 2 => 2 3 => 3 4 => 4 'universe' => Set::Scalar::Universe=HASH(0xc7b830) 'elements' => HASH(0xc87490) 1 => 1 2 => 2 3 => 3 4 => 4 'null' => Set::Scalar::Null=HASH(0xc7c200) 'universe' => Set::Scalar::Universe=HASH(0xc7b830) -> REUSED_ADDRESS 'universe' => undef DB<5> $y = $x DB<6> x $x += 5 Operation "=": no method found, argument in overloaded package Set::Scalar at (eval 16)[/mathworks/hub/share/apps/BuildTools/Linux/glibc-2.3.6/x86_64/perl/perl-5.8.8-tmw-026/lib/5.8.8/perl5db.pl:638] line 2. DB<7> x $x 0 Set::Scalar=HASH(0xcedb30) 'elements' => HASH(0xa5c960) 1 => 1 2 => 2 3 => 3 4 => 4 'universe' => Set::Scalar::Universe=HASH(0xc7b830) 'elements' => HASH(0xc87490) 1 => 1 2 => 2 3 => 3 4 => 4 'null' => Set::Scalar::Null=HASH(0xc7c200) 'universe' => Set::Scalar::Universe=HASH(0xc7b830) -> REUSED_ADDRESS 'universe' => undef DB<8> $y = 1 DB<9> x $x += 5 0 Set::Scalar=HASH(0xcedb30) 'elements' => HASH(0xa5c960) 1 => 1 2 => 2 3 => 3 4 => 4 5 => 5 'universe' => Set::Scalar::Universe=HASH(0xc7b830) 'elements' => HASH(0xc87490) 1 => 1 2 => 2 3 => 3 4 => 4 5 => 5 'null' => Set::Scalar::Null=HASH(0xc7c200) 'universe' => Set::Scalar::Universe=HASH(0xc7b830) -> REUSED_ADDRESS 'universe' => undef DB<10> Note that while '+=' breaks, '+' continues to work: DB<10> $y = $x DB<11> x $x += 6 Operation "=": no method found, argument in overloaded package Set::Scalar at (eval 22)[/mathworks/hub/share/apps/BuildTools/Linux/glibc-2.3.6/x86_64/perl/perl-5.8.8-tmw-026/lib/5.8.8/perl5db.pl:638] line 2. DB<12> x $x + 6 0 Set::Scalar=HASH(0xa5f630) 'elements' => HASH(0xcc44b0) 1 => 1 2 => 2 3 => 3 4 => 4 5 => 5 6 => 6 'null' => undef 'universe' => Set::Scalar::Universe=HASH(0xc7b830) 'elements' => HASH(0xc87490) 1 => 1 2 => 2 3 => 3 4 => 4 5 => 5 6 => 6 'null' => Set::Scalar::Null=HASH(0xc7c200) 'universe' => Set::Scalar::Universe=HASH(0xc7b830) -> REUSED_ADDRESS 'universe' => undef DB<13>

Thu Jan 15 17:21:45 2009 jloverso [...] mathworks.com - Status changed from 'new' to 'open'

Thu Jan 15 17:22:46 2009 jloverso [...] mathworks.com - Correspondence added

I didn't mean to change the status to 'open'. I thought that link would open another ticket. (blush)

Thu Jan 15 17:22:47 2009 jloverso [...] mathworks.com - Status changed from 'open' to 'new'

Thu Jan 15 18:06:57 2009 jloverso [...] mathworks.com - Correspondence added

From:

jloverso [...] mathworks.com

This describes what causes this problem: http://www.perlmonks.org/?node_id=33772 And it's also described in the 'overload' pod in the sections 'Copy Constructor' and 'Metaphor clash' (but the above is much more straightforward). The answer as described above is to additionally provide an overload for '=' that does a clone operation. The intent is to make it work like this: $a += 1; $b = $a; # $b and $a point to same ref $a += 1; # clone $a and point to new ref, then invoke '+' overload. Unfortunately, this doesn't help my original problem, though. Where I came across this problem was in code that held several Set::Scalar objects inside another class. I had the logical equivalent of: sub getRunning {return shift->{running}} # same for getFinished and then I used this as: $running = $scoreboard->getRunning; $finished = $scoreboard->getFinished; ... $finished += $running; A 'clone' solution won't help me at all, because I want $finished to be the same object inside the '$scoreboard' object. My only recourse is to change the += to this, which doesn't read as nicely: $finished->insert($running->members);

Tue Mar 31 12:09:35 2009 JHI [...] cpan.org - Status changed from 'new' to 'resolved'