Re: Learning about Arrays and Hashes - printing pieces of them

[Your Mother]

You have an error in the LOOKUP hashref. Here’s a simplified version that will output what you expect–

use strict;
use warnings;
my $rec = { TEXT      => "Fred loves Ethel",
            SEQUENCE  => [ 13, 27, 47, 98 ],
            LOOKUP    => { cars => 'Buick', dog => 'hound' } };

print $rec->{TEXT}, "\n",
    $rec->{SEQUENCE}[0], "\n",
    $rec->{LOOKUP}{dog}, "\n";

Notes — Find the difference between your LOOKUP and mine. Always use strict and warnings (at least when starting). You can pass a list of things to print so only one is necessary. The newlines generally have to be asked for as well. Welcome to the monastery and good luck with Perl! It’s a terrific language.

(Update: LanX usually welcomes newcomers… Sorry you had to settle for me. :P)

[Anonymous Monk]

Hi Mom!

I see my dog forgot to point to my hound.... I was missing the > pointing to hound. Thank you!

What happens when I try:

print $rec -> [Buick], "\n";

Does that just print "Buick" or does it print a 0? I didn't find a specific example of that so I was wondering how I find the value Buick.

Could I do something like this:

my $favoriteCar = $rec->{LOOKUP}[0];
print "My favorite car is ", $favoriteCar, "\n";

Thank you!

Raye Ann

[NetWallah]

You can answer these questions by running the code yourself, under the perl built-in debugger.

Just run you rprogam like this:

perl -d <Your-program-file-name>

Inside the debugger prompt , use the "h" (help) command , using "x" check the values of the variables.

Note: You need to FIRST use the "s" command to get the $rec variable initialized.

Here are the results of running your program - it includes answers to your questions:

  DB<1> s
main::(junk.pl:10):     print $rec->{TEXT},"\n",
main::(junk.pl:11):        $rec->{SEQUENCE}[0],"\n",
main::(junk.pl:12):      $rec->{LOOKUP}{"dog"},"\n";
  DB<1> x  $rec -> [Buick]
Not an ARRAY reference at (eval 7)[/usr/lib/perl5/5.10.0/perl5db.pl:63
+8] line 2.
  DB<2> x  $rec -> {LOOKUP} -> {cars}
0  'Buick'
  DB<3> x  $rec -> {LOOKUP} [0]
Not an ARRAY reference at (eval 9)[/usr/lib/perl5/5.10.0/perl5db.pl:63
+8] line 2.
  DB<4> x  $rec -> {LOOKUP} {dog}
0  'hound'
  DB<5> q