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Postings from June 2012
On 2012-06-26 demerphq wrote:
> On 25 June 2012 22:51, Father Chrysostomos via RT
> <perlbug-followup@perl.org> wrote:
> > Allowing an empty list provides a clear benefit and makes things
> > more consistent. What problems could it cause?
>
> It would make debugging difficult. Consider generated code, etc.
How would it make debugging more difficult?
> I am with Reini on this one, and ill drag in Larry too. Im pretty sure
> if Larry thought that
>
> my ();
>
> should be legal it already would be.
See
http://perl5.git.perl.org/perl.git/blob/09bef84370e90d727656ea11ba5ee8be80e361d3:/perly.y#l661
655 myattrterm: MY myterm myattrlist
656 { $$ = my_attrs($2,$3); }
657 | MY myterm
658 { $$ = localize($2,$1); }
659 ;
660
661 myterm : '(' expr ')'
662 { $$ = sawparens($2); }
663 | '(' ')'
664 { $$ = sawparens(newNULLLIST()); }
The "myterm : '(' ')'" branch explicitly allows this syntax. It was
added to perl in 1999. The fact that other passes of the compiler can't
handle the generated structure is a bug (probably just an oversight,
since the fix is literally four tokens long).
> That my behaves "a little different" isn't new, we allow the special
> use of undef in a my() declaration:
>
> my ($x,undef,$y)= @l;
>
> I contend that allowing my (); would make debugging difficult. I also
> contend that it is meaningless/absurd to "declare zero items".
To me your argument feels like you'd also want to make m/foo|/
invalid because it would be meaningless to "match zero characters".
(And by extension 0 is not an actual number, because it would be
meaningless to "count zero items".) In other words, I don't find it
convincing.
> Does C allow you to write:
>
> int;
>
> ?
No, but it allows 'int ()'. It means something entirely different but
that's because C is not Perl. (Does C allow you to write 'printf("%d",
int i++)'?)
Lukas
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