Re: Passing Arrays to Subroutines

You're not paying attention to what you've asked perl to do. You say:

If I replace the 2 with 0 I get what looks like the first line of the data file printed but I expected to get just the first item

Yet, looking at your code, you read all of the lines of your file into an array, then return that array from your readdata() subroutine. In your main bit of code, you print out the 3rd item in that array of lines. So, of course you're going to get an entire line of data!

What you apparently want to do is subsequently split each line on whitespace (maybe?) and then print out the bits of the line that interest you.

...
my @lines = readdata();
foreach my $line (@lines) {
   my @fields = split ' ', $line;
   print $fields[2];
}
...
[download]

It would greatly help your cognitive processes if you chose better names for your subroutines and variables; "data" is just too generic. Use the variable names to describe what the data are.

PerlJam

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Re: Re: Passing Arrays to Subroutines by shemyaza (Novice) on Nov 26, 2003 at 16:46 UTC
Thanks for your help. I copied part of the code from a book which wasn't too clear on whether the array items would be split on whitespace or be lines. I see now that they are lines. What you have suggested is pretty much what I had in mind. I take your point about variable names, I guess I wasn't being very imaginative :-). Cheers S.	[reply]
3Re: Passing Arrays to Subroutines by jeffa (Bishop) on Nov 26, 2003 at 18:40 UTC
If you are developing generic subroutines, then the names inside your subroutines aren't bad, but the fact that you hard code the name of the file is. If you pass the in the name of the file as an argument to the sub, then you will have some reusable subroutines: `sub file_to_list { my $name = shift or die "must have name to read"; open (FILE, '<', $name) or die "can't read from $name: $!"; chomp(my @data = <FILE>); return @data; } sub list_to_file { my $name = shift or die "must have name to write"; open (FILE, '>', $name) or die "can't write to $name: $!"; print FILE "$_\n" for @_; } my @foo = file_to_list('file.in'); print "$_\n" for @foo; list_to_file('file.out',@foo);` [download] jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l]