Hello everyone,
I was reading about sort in the camel (3rd ed., p. 793) and I found that
sorting subroutines must be placed in the same package as they are called
from since $a and $b are package globals. Therefore, sorting functions
cannot be "modulized" without help. The camel suggests two workarounds:
qualifying $a and $b with the package name of the caller, and passing $a and
$b as arguments (which also requires prototyping the sorting function and
declaring $a and $b as lexicals).
I was able to get the second method to work, but not the first. Could
someone please explain (and provide an example of) how the package name of
the calling function can be used to qualify $a and $b, as suggested in the
camel? I tried playing around with the *{foo}{PACKAGE} and *{foo}{NAME}
notation, but without success.
On a related note, is one of these two methods preferred over the other?
Here are the tests I've tried. Both give the expected output:
unsorted: 1 9 5 10 2
sorted: 1 2 5 9 10
** sort routine in same package **
SORTTEST.PL:
use strict;
use warnings;
my @nums = qw( 1 9 5 10 2 );
print "unsorted: @nums\n";
@nums = sort numerically @nums;
print "sorted: @nums\n";
sub numerically
{
$a <=> $b;
}
** sort routine in a separate package **
SORTTEST.PL:
use strict;
use warnings;
use Sort_Numerically;
my @nums = qw( 1 9 5 10 2 );
print "unsorted: @nums\n";
@nums = sort numerically @nums;
print "sorted: @nums\n";
SORT_NUMERICALLY.PM:
package Sort_Numerically;
use strict;
use warnings;
use Exporter;
our @ISA = ( "Exporter" );
our @EXPORT = ( "numerically" );
sub numerically ($$)
{
my ( $a, $b ) = @_;
$a <=> $b;
}
Thanks in advance,
Bob
Robert Freimuth, PhD
Post-Doctoral Fellow
Washington University School of Medicine
Department of Internal Medicine
Division of Molecular Oncology
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