Question

I am having some problem with my perl. I hashed a key to an array. Now I want to change things in the array for each key. But I can’t find out how this works :

open(DATEBOOK,"<sample.file");

@datebook = <DATEBOOK>;

$person = "Norma";

foreach(@datebook){
    @record = ();
    @lines = split(":",$_);

        $size = @lines;
        for ($i=1; $i < $size; $i++){
            $record[$i-1] = $lines[$i];
        }
    $map{$lines[0]}="@record";  

}

for(keys%map){ print $map{$_}};

The datebook file :

Tommy Savage:408.724.0140:1222 Oxbow Court, Sunnyvale,CA 94087:5/19/66:34200
Lesle Kerstin:408.456.1234:4 Harvard Square, Boston, MA 02133:4/22/62:52600
JonDeLoach:408.253.3122:123 Park St., San Jose, CA 94086:7/25/53:85100
Ephram Hardy:293.259.5395:235 Carlton Lane, Joliet, IL 73858:8/12/20:56700
Betty Boop:245.836.8357:635 Cutesy Lane, Hollywood, CA 91464:6/23/23:14500
William Kopf:846.836.2837:6937 Ware Road, Milton, PA 93756:9/21/46:43500
Norma Corder:397.857.2735:74 Pine Street, Dearborn, MI 23874:3/28/45:245700
James Ikeda:834.938.8376:23445 Aster Ave., Allentown, NJ 83745:12/1/38:45000
Lori Gortz:327.832.5728:3465 Mirlo Street, Peabody, MA 34756:10/2/65:35200
Barbara Kerz:385.573.8326:832 Ponce Drive, Gary, IN 83756:12/15/46:268500

I tried $map{$_}[1], but that doesn’t work. Can anyone give me an example on how this works 🙂 ?

thanks!

Answer 1

First, use strict and use warnings. Always.

Assuming what you want is a hash of arrays, do something like this:

use strict;
use warnings;

open my $datebookfh, '<', 'sample.file' or die $!;
my @datebook = <$datebookfh>;

my %map;
foreach my $row( @datebook ) { 
    my @record = split /:/, $row;
    my $key = shift @record;   # throw out first element and save it in $key

    $map{$key} = \@record;
}

You can test that you have the correct structure by using Data::Dumper:

use Data::Dumper;
print Dumper( \%map );

The \ operator takes a reference. All hashes and arrays in Perl contain scalars, so compound structures (e.g. hashes of arrays) are really hashes of references to arrays. A reference is like a pointer.

Before going further, you should check out:

• Perl reference tutorial
• Arrays of arrays
• Perl Data Structure Cookbook