Re: Array manipulation

Since you claim to be new (like me), some comments on your code:

my $i="";
my $t="";
my @data="";
[download]

Variables that have never been used have the special undef value. What happens if you use a variable that has the undef value? Nothing serious

If you use it as a number it takes on the value 0 (zero). If you use it as a string it takes on the value of an empty string. You do not have to set them to "". You use $i and $t as numeric values in your code so setting them to "" is kinda confusing.

Setting the array @data to "" does not make much sense for an array either. If you want to empty an array assign it to an empty list:

my @data = ();
[download]

But a new array starts out this way anyway.

Now lets take a look at your loops...

$lines=scalar@data/4;

for ($t=1; $t<=$lines; $t++) {

for ($i=1; $i<=4; $i++) {

    $items=shift(@data);
   
    print $items;
}
[download]

($t=1; $t<=$lines; $t++) works, but it is more common to start with $t=0 and use $t<$lines as the termination.

Getting used to this will prevent you from getting into trouble when indexing through arrays which start with an index of zero. It also prevents a finger-flub of forgetting the = in the condition.

Lou

Update: Oh, one more thing that is good to get used to when you are new. Besides using use strict;, also consider...

use warnings;    # flags many questionable constructs
use diagnostics; # makes error messages much more understandable
[download]

Lou

Comment on Re: Array manipulation Select or Download Code

Replies are listed 'Best First'.
Re^2: Array manipulation by wfsp (Abbot) on May 19, 2005 at 08:31 UTC
A minor point on your update. The OP's code starts with: `#!/usr/bin/perl -Tw` [download] So warnings are on. Taint mode is also set which will also contribute to davido's "clean and healthy life". Note: I am of course assuming that the w wasn't added after you posting.	[reply] [d/l]
Re^2: Array manipulation by loop362 (Pilgrim) on May 19, 2005 at 01:38 UTC
Thank you for advice Lou. BBEdit creates a sytax error if I don't declare the variables as empty, that is why I do it that way. JWG	[reply]
Re^2: Array manipulation by scmason (Monk) on May 19, 2005 at 16:36 UTC
Good points, but I would like to make an argument why it is a good practice to intiialize variables by hand. Readability - traceability is important. Since Perl is not a strongly typed language, it is often more difficult to understand the authors intentions on a given variable. In C/C++/Java, you know what a variable will be used for not only by its name, but also by its type. By initializing a variable to the empty string or 0, you let the reader know more about your intended purposes with the variable. `"Never take yourself too seriously, because everyone knows that fat birds dont fly" -FLC` [download]	[reply] [d/l]