Solved

Passing 2D array to a sub()

Posted on 2008-06-20
5
246 Views
Last Modified: 2010-03-05
Hi,

I read a 2d array from file, so I have something like:

    @my2dArray[5][5];

I can iterate over it, ok. I want to pass it to a sub routine, like:

    pass2dArray(my2dArray);

    sub pass2dArray()
    {
        my (@array) = @_;
    }

Am I passing a copy of the 2d array to the function, or is it just referencing the original array?

Then, if I want to pass a single row of the array to another sub, how would I do that? I was hoping something like:

    sub pass2dArray()
    {
        my (@array) = @_;
   
        # pass row 2:
        passOneRowOf2dArray(2);
       
        # etc
        passOneRowOf2dArray(4);
    }

    sub passOneRowOf2dArray()
    {
        my (@row) = @_;
        for (my $i = 0; $i < @row; $i++) {
           ...
        }
    }
   

Thanks
0
Comment
Question by:DJ_AM_Juicebox
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
5 Comments
 
LVL 39

Expert Comment

by:Adam314
ID: 21831510
With this:
    pass2dArray(@my2dArray);
You are passing a copy of the original array, which contains references to the 2nd dimension.  You are not passing copies of the 2nd dimension.  Meaning, if your pass2dArray function, if you add or remove elements from @array, this will not be affected in @my2dArray.  But if you change, add or remove elements from any of the rows, this will be affected in @my2dArray.

To pass one row as a reference, you would use:
    passOneRowOf2dArray($array[2]);    #passes reference to second row
To pass one row as an array (not a reference), you would use:
    passOneRowOf2dArray(@{$array[2]});

If you want to pass a copy of a structure like this, you can use the Storable module's dclone function:
http://search.cpan.org/~ams/Storable-2.18/Storable.pm
0
 

Author Comment

by:DJ_AM_Juicebox
ID: 21831577
>>To pass one row as a reference, you would use:
    passOneRowOf2dArray($array[2]);    #passes reference to second row


Ok, that's just what I put, but how do you recover the reference to the single row in the function? Like:

    sub passOneRowOf2dArray()
    {
        my @row = shift;
    }

???

That doesn't work though...

Thanks

0
 
LVL 39

Accepted Solution

by:
Adam314 earned 500 total points
ID: 21831919

sub passOneRowOf2dArray {
    my $ref_to_row = shift;    #get reference
    
    #changes to $ref_to_row will show up in the original array
    print "first value=$ref_to_row->[0]\n";
    print "all values=" . join(", ", @{$ref_to_row}) . "\n";
    
    #Get as a regular array, makes a copy
    my @array_copy = @{$ref_to_row};
    
    #changes to @array_copy will not show up in the original array
    print "first value=$array_copy[0]\n";
    print "all values=" . join(", ", @array_copy) . "\n";
}

Open in new window

0
 
LVL 39

Expert Comment

by:Adam314
ID: 21831928
This website might be helpful:
http://perldoc.perl.org/perlreftut.html
0
 

Author Comment

by:DJ_AM_Juicebox
ID: 21834512
Perfect, thanks.
0

Featured Post

Enroll in June's Course of the Month

June's Course of the Month is now available! Every 10 seconds, a consumer gets hit with ransomware. Refresh your knowledge of ransomware best practices by enrolling in this month's complimentary course for Premium Members, Team Accounts, and Qualified Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have been pestered over the years to produce and distribute regular data extracts, and often the request have explicitly requested the data be emailed as an Excel attachement; specifically Excel, as it appears: CSV files confuse (no Red or Green h…
There are many situations when we need to display the data in sorted order. For example: Student details by name or by rank or by total marks etc. If you are working on data driven based projects then you will use sorting techniques very frequently.…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Six Sigma Control Plans

705 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question