Set Array Columns to 0

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

Hello Monks, I am attempting to set the value of blank elements in an array to zero. How can I do this? The input looks like this:

 
Thurs,July,5,2012,123,456,789
Thurs,July,5,2012,123,456,789,Fri,July,6,2012
[download]

Here is my code

my $line;
my ($dow,$mon,$day,$year,$num1,$num2,$num3,$dow2,$mon2,$day2,$year2) =
+ "";
foreach $line (@array){
    ($dow,$mon,$day,$year,$num1,$num2,$num3,$dow2,$mon2,$day2,$year2) 
+= split /[,]/, $line; 
    print "$dow2\n";
[download]

I would like to be able to print $dow2 through $year2 but I am getting the error "Use of uninitialized value $dow2 in print..." What am I doing wrong here?

Comment on Set Array Columns to 0 Select or Download Code

Replies are listed 'Best First'.
Re: Set Array Columns to 0 by jethro (Monsignor) on Jul 05, 2012 at 16:41 UTC
Your second line will only initialize the first variable $dow with "", all the other variables will be set to undef The simplest code to make it work is to extend the list on the right hand side of line 4 so that it will always be enough to fill all variables even if split would return the empty list: `($dow,$mon,$day,$year,$num1,$num2,$num3,$dow2,$mon2,$day2,$year2)= ( s +plit(/[,]/, $line),("") x 11 );` [download] Note that 'x' is an operator that in this case produces a list of 11 empty strings. Naturally you could also use 0 instead of "".	[reply] [d/l]
Re^2: Set Array Columns to 0 by Anonymous Monk on Jul 05, 2012 at 21:18 UTC
Is there any way to fill in the missing area (the top line where the date is) with comma-separated 0's? I tried your example and it does not print with zeros. Thank you.	[reply]
Re^3: Set Array Columns to 0 by frozenwithjoy (Priest) on Jul 06, 2012 at 07:08 UTC
Just replace the quotes in `("") x 11` with your placeholder of choice.	[reply] [d/l]
Re: Set Array Columns to 0 by toolic (Bishop) on Jul 05, 2012 at 16:33 UTC
Your 1st input line only has 7 columns, but $dow2 corresponds to the 8th column. You get the warning message because split sets the 8th-11th columns to the undefined value. Perhaps you want: `print "$dow2\n" if defined $dow2;` [download]	[reply] [d/l]
Re: Set Array Columns to 0 by brx (Pilgrim) on Jul 05, 2012 at 16:41 UTC
When you split the line, the result can be a list which contains less elements than you are expecting. `Thurs,July,5,2012,123,456,789` : here you'll obtain 7 elements, no more. So, do not trust the input and don't forget to chomp your lines. Here, I'm using an additional list of 11 empty string ("" is not undef) to be sure that all (11) variables are defined. `#!perl use strict; use warnings; my @array=<DATA>; chomp @array; my $line; my ($dow,$mon,$day,$year,$num1,$num2,$num3,$dow2,$mon2,$day2,$year2); foreach $line (@array){ ($dow,$mon,$day,$year,$num1,$num2,$num3,$dow2,$mon2,$day2,$year2) += ((split /[,]/, $line),("")x11); print "$dow2\n"; } __DATA__ Thurs,July,5,2012,123,456,789 Thurs,July,5,2012,123,456,789,Fri,July,6,2012` [download]	[reply] [d/l] [select]