At 2:22 PM -0500 1/26/01, Vic Norton wrote:
>How do you package a sorting subroutine for use with sort? That's
>what I don't understand.
[snip]
>I assume that I am losing $a and $b when my subroutine resides in the
>external package VTN::Utilities, but I don't know what to do about it.
The global variables $a and $b are temporarily set in the package
where the sort routine was compiled. So, if your sort subroutine is
defined in an external package, to access the sort variables you'll
need to make $a and $b properly qualified over there.
I just scanned what Ken Williams posted, which was good. Here's
another way to correctly handle the package scoping. Use the
caller() function in the subroutine definition in the external
package:
#!perl -w
package Utils::Sort;
use strict;
use vars qw/@ISA @EXPORT @EXPORT_OK $VERSION/;
$VERSION='0.1';
@ISA = qw{Exporter};
@EXPORT = qw{&case_order};
@EXPORT_OK = qw{};
sub case_order {
my ($pkg) = caller;
no strict 'refs';
my $a = ${$pkg.'::a'};
my $b = ${$pkg.'::b'};
# OK, now we can sort...
$a cmp $b
}
1;
__END__
The trick is to use the first value returned by caller(), the package
name, to form the compound "fully qualified" names for $a and $b. The
sub-pretty stuff there, ${$pkg.'::a'}, runs the risk of being
interpreted as a soft reference, hence the local muting of the strict
coding scolds.
After those four lines, $a and $b may be used as in any other sort
sub, even though they're really locally scoped copies of the real
things.
Now in another package, of any name:
#!perl -w
package Arbitrary; # Or none...
use Utils::Sort;
use strict;
my @list = qw{a G E k H b P y s A};
print sort case_order @list;
__END__
# AEGHPabksy
HTH
1;
--
- Bruce
__bruce_van_allen__santa_cruz_ca__
