On Mon, Jan 3, 2011 at 8:24 AM, Sunita Rani Pradhan
<sunita.prad...@altair.com> wrote:
> How can I define default arguments in Perl subroutine? Can
> anybody explain with examples?
I would probably do something like:
#!/usr/bin/env perl
use strict;
use warnings;
sub foo
{
my $bar = shift || 'default bar';
my $baz = shift || 'default baz';
print "\$bar=$bar\n";
print "\$baz=$baz\n";
}
foo;
foo 'bar';
foo qw/bar baz/;
__END__
If you wanted something like named arguments, where you could specify
arguments in any order, then I'd use a hash reference instead.
#!/usr/bin/env perl
use strict;
use warnings;
# There might be a one liner to do this, but I couldn't get it
# working with hash references. :P
sub augment
{
my $first = shift;
my $second = shift;
die "Invalid argument"
unless ref $first eq 'HASH' && ref $second eq 'HASH';
for my $key (keys %$second)
{
$first->{$key} = $second->{$key} unless exists $first->{$key};
}
}
sub foo
{
my $args = shift || {};
my %defaults = (
bar => 'default bar',
baz => 'default baz'
);
die "Invalid argument" unless ref $args eq 'HASH';
# Use values in %defaults for missing values in %$args.
augment $args, \%defaults;
print "\$args->{bar}=$args->{bar}\n";
print "\$args->{baz}=$args->{baz}\n";
}
foo;
foo { bar => 'bar' };
foo { baz => 'baz' };
foo { bar => 'bar', baz => 'baz' };
foo { baz => 'baz', bar => 'bar' };
__END__
If you're new to Perl then there are many topics that you'll need to
read up on. For operators, like ||, q//, and qw//, read `perldoc
perlop`. For references, try `perldoc perlref`. For passing arguments
to subroutines, try `perldoc perlsub`. For built-in subroutines that
you don't know about, try `perldoc -f name`. For example, `perldoc -f
shift` and `perldoc -f ref`.
--
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