Bug #52984 for Quantum-Superpositions: Using "any" and "all" with "defined"

Tue Dec 22 18:47:01 2009 ifomichev [...] cpan.org - Ticket created

CC:	rakudobug [...] perl.org
Subject:	Using "any" and "all" with "defined"

Hello, I'm not sure if it is a bug or a forced misfeature, but the following code does not work as I'd expect: $ perl -MQuantum::Superpositions -le 'print defined all(undef, 0, 1);' 1 $ perl -MQuantum::Superpositions -le 'print defined any(undef, undef);' 1 BTW, Perl 6 (Rakudo "Seoul") does the same: $ perl6 -e 'say defined all(undef, 0, 1)' 1 $ perl6 -e 'say defined any(undef, undef)' 1 Could you please comment this issue?

Tue Dec 22 23:41:59 2009 damian [...] conway.org - Correspondence added

Subject:	Re: [rt.cpan.org #52984] Using "any" and "all" with "defined"
Date:	Wed, 23 Dec 2009 15:41:23 +1100
To:	bug-Quantum-Superpositions [...] rt.cpan.org
From:	Damian Conway <damian [...] conway.org>

Hi Ivan, Show quoted text

> Hello, I'm not sure if it is a bug or a forced misfeature, but the > following code does not work as I'd expect: > > $ perl -MQuantum::Superpositions -le 'print defined all(undef, 0, 1);' > 1 > $ perl -MQuantum::Superpositions -le 'print defined any(undef, undef);' > 1

This is an unavoidable misfeature. Perl 5 does not allow us to overload the 'defined' builtin, so we're stuck with the default behaviour, which treats a superposition object like any other object (i.e. as being defined). :-( Show quoted text

> > BTW, Perl 6 (Rakudo "Seoul") does the same: > > $ perl6 -e 'say defined all(undef, 0, 1)' > 1 > $ perl6 -e 'say defined any(undef, undef)' > 1

Those are definitely bugs. Though Perl 6 changed recently and 'undef' no longer exists. You'd have to write: say defined all(Mu, 0, 1) say defined any(Mu, Mu) Damian

Tue Dec 22 23:41:59 2009 The RT System itself - Status changed from 'new' to 'open'

Wed Dec 23 01:15:50 2009 ifomichev [...] cpan.org - Correspondence added

On Tue Dec 22 23:41:59 2009, damian@conway.org wrote: Show quoted text

> This is an unavoidable misfeature. Perl 5 does not allow us to

overload the Show quoted text

> 'defined' builtin, so we're stuck with the default behaviour, which treats > a superposition object like any other object (i.e. as being defined). :-(

Is there a chance, that we'll be allowed in 5.12? ;-)

Wed Dec 23 02:59:25 2009 damian [...] conway.org - Correspondence added

Subject:	Re: [rt.cpan.org #52984] Using "any" and "all" with "defined"
Date:	Wed, 23 Dec 2009 18:58:49 +1100
To:	bug-Quantum-Superpositions [...] rt.cpan.org
From:	Damian Conway <damian [...] conway.org>

Show quoted text

>> Perl 5 does not allow us to overload the 'defined' builtin, so we're >> stuck with the default behaviour, which treats a superposition object >> like any other object (i.e. as being defined). :-(

Show quoted text

> Is there a chance, that we'll be allowed in 5.12? ;-)

Very little chance, I fear. defined() doesn't have a prototype that's expressible in Perl 5 itself, so there's no way to override it. It would require a significant change to the prototype syntax to allow the various argument types that defined() supports. Unfortunately, there's no sign that 5.12 will have any such additions. Damian

Wed Dec 23 06:09:05 2009 ifomichev [...] cpan.org - Correspondence added

Damian, thank you for your comments. By the way, it is possible to provide a workaround for now, e. g. use Quantum::Superpositions; package Quantum::Superpositions::Disj; sub defined { foreach ($_[0]->eigenstates) { return 1 if defined; } return ''; } package Quantum::Superpositions::Conj; sub defined { foreach (@{$_[0]}) { return '' if !defined; } return 1; } package main; print all(undef, 0, 1)->defined, "\n"; print any(undef, undef)->defined, "\n";

Wed Dec 23 12:52:38 2009 ifomichev [...] cpan.org - Cc rakudobug@perl.org deleted

Wed Dec 23 12:52:55 2009 ifomichev [...] cpan.org - Correspondence added

On second thought, the algorithm should be a little bit more complex to properly process nested junctions, something like: use Quantum::Superpositions; package Quantum::Superpositions::Disj; sub defined { foreach ($_[0]->eigenstates) { return 1 if eval { $_->isa($_, 'Quantum::Superpositions') } ? $_->defined : defined; } return ''; } package Quantum::Superpositions::Conj; sub defined { foreach (@{$_[0]}) { return '' if eval { $_->isa($_, 'Quantum::Superpositions') } ? !$_->defined : !defined; } return 1; }

Wed Dec 23 13:46:49 2009 ifomichev [...] cpan.org - Correspondence added

On Wed Dec 23 12:52:55 2009, IFOMICHEV wrote: Show quoted text

> return 1 if eval { $_->isa($_, 'Quantum::Superpositions') } > ? $_->defined : defined;

Sorry, a bug. return 1 if eval { $_->isa('Quantum::Superpositions') } ? $_->defined : defined;