YARQ:Yet another reference question

snafu has asked for the wisdom of the Perl Monks concerning the following question:

I have been spending the last couple of hours on learning more about references (more out of necessity rather than curiosity) and I just haven't been able to find an answer to the situation I am finding myself in.

if ( &check_for_valid_conf($config_file) ) {

    my (@class, @rules) = &parse_conf($config_file);
    print "class has $#class elements and rules has $#rules elements\n
+";
    print join("\n",@class),"\n";
}

sub parse_conf {
    ...
    return(@class,@ind_rules);
}
[download]

Ok. What we have here is a perfect example of why I need to use or would prefer to use references. This is good cuz when I started coding in Perl 6 months ago I couldn't even think of a reason why I would need to use references. But, finally, I have a reason now...and I am falling short of the best way to do it in this case.

Briefly, what I would like to do is pass the two arrays being returned from the sub routing to be two arrays in main::. That obviously can't be done the way it is written above because the return() will crunch the arrays into one array leaving me with only one array. :P

So, what would be the best way to pass those two arrays from the subroutine to the caller to return two arrays?

I've tried the following code to no avail. I admit, I am kind of shooting in the dark because I am still trying to grasp using references properly.

Here is some of the things I tried:

my ($arr1, $arr2) = \&sub(arg);
print join("\n",@$arr1);
print join("\n",@$arr2);

sub sub {
    @arr1 = qw(foo bar quux);
    @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}

perl -Mstrict -e '
my ($arr1, $arr2) = \&sub("arg");
print join("\n",@$arr1);
print join("\n",@$arr2);

sub sub {
    my @arr1 = qw(foo bar quux);
    my @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}'
Not an ARRAY reference at -e line 3.

perl -Mstrict -e '
my (@arr1, @arr2) = &sub("arg");
print join("\n",@arr1);
print join("\n",@arr2);

sub sub {
    my @arr1 = qw(foo bar quux);
    my @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}'
ARRAY(0x10f07c)
ARRAY(0x10f0c4)

perl -Mstrict -e '
my (@arr1, @arr2) = &sub("arg");
print join("\n",@{$arr1}),"\n\n";
print join("\n",@{$arr2}),"\n";

sub sub {
    my @arr1 = qw(foo bar quux);
    my @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}'
Global symbol "$arr1" requires explicit package name at -e line 3.
Global symbol "$arr2" requires explicit package name at -e line 4.
Execution of -e aborted due to compilation errors.

perl -Mstrict -e '
my (@arr1, @arr2) = &sub("arg");
print join("\n",@arr1),"\n\n";
print join("\n",@arr2),"\n";

sub sub {
    my $arr1 = \qw(foo bar quux);
    my $arr2 = \(1,2,3);

    return($arr1,$arr2);
}'
SCALAR(0x10f0d0)
SCALAR(0x10f100)


perl -Mstrict -e '
my ($arr1, $arr2) = &sub("arg");
print join("\n",@$arr1),"\n\n";
print join("\n",@$arr2),"\n";

sub sub {
    my $arr1 = \qw(foo bar quux);
    my $arr2 = \(1,2,3);

    return($arr1,$arr2);
}'
Not an ARRAY reference at -e line 3.


perl -Mstrict -e '
print &sub("arg"),"\n";
 
sub sub {                    
    my $arr1 = \qw(foo bar quux);
    my $arr2 = \(1,2,3);
                        
    return($arr1,$arr2);
}'
SCALAR(0x1061d8)SCALAR(0x10613c)


perl -Mstrict -e '
print @{&sub("arg")},"\n";

sub sub {
    my $arr1 = \qw(foo bar quux);
    my $arr2 = \(1,2,3);

    return($arr1,$arr2);
}'
Not an ARRAY reference at -e line 2.


perl -Mstrict -e '
print ${&sub("arg")},"\n";

sub sub {
    my $arr1 = \qw(foo bar quux);
    my $arr2 = \(1,2,3);

    return($arr1,$arr2);
}'
3

OOH, getting closer! :)


perl -Mstrict -e '
print @{&sub("arg")},"\n";

sub sub {
    my @arr1 = qw(foo bar quux);
    my @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}'
123


GETTING CLOSER YET! :)


perl -Mstrict -e '
my (@arr1,@arr2) = @{&sub("arg")};
print join(", ",@arr1),"\n\n";print join(", ",@arr2),"\n";
sub sub {
    my @arr1 = qw(foo bar quux);
    my @arr2 = (1,2,3);

    return(\@arr1,\@arr2);
}'
1, 2, 3
[download]

Hmm, and I am still having problems. So, I can get the second array out now. How come the first one isn't getting out? :)

Please be gentle, fellow monks :]

_ _ _ _ _ _ _ _ _ _
- Jim
Insert clever comment here...

Comment on YARQ:Yet another reference question Select or Download Code

Replies are listed 'Best First'.
Re: YARQ:Yet another reference question by derby (Abbot) on Mar 13, 2002 at 19:35 UTC
so close, `my ($arr1, $arr2) = &sub(); print join("\n",@$arr1); print join("\n",@$arr2); sub sub { my @arr1 = qw(foo bar quux); my @arr2 = (1,2,3); return(\@arr1,\@arr2); }` [download] note: you don't have to my the arrays in your function, it's just nicer to not have globals hanging around (also, I'm not to crazy about a subroutine named "sub" - perfectly legal but a little too wacky). -derby	[reply] [d/l]
Re: YARQ:Yet another reference question by PrimeLord (Pilgrim) on Mar 13, 2002 at 19:36 UTC
You can return the arrays as ref's for us in main like this. `my ($arr1,$arr2) = &sub(); sub { return \(@arr1, @arr2); }` [download] And then you can access the arrays with: `$arr1->[0] $arr2->[1]` etc. HTH -Prime Update:Beaten to the punch again :)	[reply] [d/l] [select]
Re: YARQ:Yet another reference question by particle (Vicar) on Mar 13, 2002 at 19:37 UTC
you show great initiative by doing so much to understand references. with this in mind, i thought rather than coding an answer for you i'd point you to the docs! enjoy ;) ~Particle	[reply]
Re: YARQ:Yet another reference question by Juerd (Abbot) on Mar 13, 2002 at 19:55 UTC
How to RTFM perlref perlreftut (Damn it! Someone PLEASE update this site's documentation! In the meantime, `perldoc perlreftut`) Returning two arrays.. (Super Search) Good luck, and have fun reading. U28geW91IGNhbiBhbGwgcm90MTMgY W5kIHBhY2soKS4gQnV0IGRvIHlvdS ByZWNvZ25pc2UgQmFzZTY0IHdoZW4 geW91IHNlZSBpdD8gIC0tIEp1ZXJk	[reply]