[ILUG] Silly perl question

[Cian Brennan]

myswap is declared within the package main, and x and y are declared at the top
level of main. So they're accessible by everything in main.
On Thu, Aug 28, 2008 at 11:25:50AM +0100, Braun Brelin wrote:
> Cian,
> 
> Yes, but my point is that I wouldn't expect the program
> to run at all.  I would have expected that within myswap, y and x would be
> local variables, and thus, with the use strict pragma enabled, that perl
> would require x and y to be declared within myswap with the 'my'
> declaration.   Otherwise, what happens to the concept of scoping?
> 
> Braun
> 
> 
> On Thu, Aug 28, 2008 at 11:18 AM, Cian Brennan <lil_cain at redbrick.dcu.ie>wrote:
> 
> > That's because they weren't defined in myswap. You're confusing local with
> > my.
> >
> > variables created with local are local to the
> > sub/package/module/loop/whatever
> > esle they're created in. You seem to want to declare $y and $x as local
> > within
> > myswap()
> > On Thu, Aug 28, 2008 at 11:14:00AM +0100, Braun Brelin wrote:
> > > The other odd thing is that the perl I'm using doesn't seem to have local
> > > vs. global variable scoping...
> > >
> > >
> > > --   Perl script --
> > > #!/usr/bin/perl
> > > use strict;
> > >
> > > my $x=1;
> > > my $y=10;
> > >
> > > myswap();
> > >
> > > sub myswap {
> > >     $y = $x;
> > > }
> > >
> > > print "y = ",$y,"\n";
> > >
> > > -------------------------------------------------------------------------
> > >
> > > Not only doesn't it complain about x and y not being
> > > defined in myswap, it goes ahead and changes the
> > > x and y defined outside the myswap function...
> > >
> > > Braun
> > >
> > >
> > >
> > > On Thu, Aug 28, 2008 at 11:10 AM, Braun Brelin <bbrelin at gmail.com>
> > wrote:
> > >
> > > > Doesn't use strict require that all variables be declared before they
> > are
> > > > used regardless of whether they're global or local?
> > > >
> > > > Braun
> > > >
> > > >
> > > >
> > > > On Thu, Aug 28, 2008 at 11:06 AM, Jimmy O'Regan <joregan at gmail.com>
> > wrote:
> > > >
> > > >> 2008/8/28 Braun Brelin <bbrelin at gmail.com>:
> > > >> > Hello all,
> > > >> >
> > > >> > I have a silly Perl question.  I'm running an Ubuntu Linux system
> > > >> (8.04),
> > > >> > with Perl 5.8.8.
> > > >> >
> > > >> > However, the 'use strict' pragma seems not to be working.  I.e. I
> > have
> > > >> the
> > > >> > following
> > > >> > Perl script:
> > > >> >
> > > >> > #!/usr/bin/perl
> > > >> >
> > > >> > use strict;
> > > >> >
> > > >> > $a=10;
> > > >> >
> > > >> > print "a = ",$a,"\n";
> > > >> >
> > > >> > This should fail miserably with an error about not having $a
> > declared,
> > > >> but,
> > > >> > unfortunately, it doesn't.  It just prints '10'.
> > > >> >
> > > >> > This isn't my normal machine so I'm not sure how Perl was built,
> > > >> although I
> > > >> > suspect
> > > >> > that it isn't anything more than a standard install.  perl -V didn't
> > > >> really
> > > >> > give me any clues.  Anything stupidly obvious that I'm missing?
> > > >>
> > > >> You've declared it as a global variable; 'my' is used to declare a
> > > >> local variable
> > > >>
> > > >> #!/usr/bin/perl
> > > >>
> > > >> use warnings;
> > > >> use strict;
> > > >>
> > > >> foo();
> > > >>
> > > >> sub foo
> > > >> {
> > > >>        $a=10;
> > > >>
> > > >>        print "a = ",$a,"\n";
> > > >> }
> > > >> print $a;
> > > >>
> > > >> gives:
> > > >> a = 10
> > > >> 10
> > > >> --
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> > > >
> > > >
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> >
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> >
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> >
> -- 
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