empty array?

Could anybody tell me why @x in the last line contains nothing? Thanks a
lot.

$filename = $ARGV[0];

open(FP, $filename);
@x=();
@y=();
$i=0;
while ($line = )
{
chomp $line;
print $line;
@words = split(/\t/, $line);

$x[$i] = $words[1];
$y[$i++] = $words[2];
}
print @x;

Re: empty array?

Ela wrote:
> Could anybody tell me why @x in the last line contains nothing? Thanks a
> lot.

Have you tried starting your program with

use strict;
use warnings;

>
> $filename = $ARGV[0];
>
> open(FP, $filename);

Perhaps this failed?
Most people would check

open my $FP, '<', $filename
or die "can't open '$filename' - $!";

> @x=();
> @y=();

my @x;
my @y;

> $i=0;
> while ($line = )
> {
> chomp $line;
> print $line;
> @words = split(/\t/, $line);

Each word in your data is separated by a single tab?
There are no leading tabs?

print "DEBUG: [", join ("], [", @words, "]\n";

>
> $x[$i] = $words[1];

@words is a zero-based array. Presumably you intended to pick out only
the second item of each line?

Perhaps there isn't a second item in your data?

> $y[$i++] = $words[2];
> }
> print @x;
>


--
RGB

Re: empty array?

Ela wrote:
> Could anybody tell me why @x in the last line contains nothing?

How do you know it contains nothing?

> Thanks a
> lot.
>
> $filename = $ARGV[0];

my $filename = $ARGV[0];

> open(FP, $filename);

open FP, '<', $filename or die "Cannot open '$filename' $!";

> @x=();
> @y=();
> $i=0;

my @x;
my @y;

> while ($line = )

while ( my $line = )

> {
> chomp $line;
> print $line;
> @words = split(/\t/, $line);

my @words = split(/\t/, $line);

> $x[$i] = $words[1];
> $y[$i++] = $words[2];

perldoc -f push

push @x, $words[1];
push @y, $words[2];

> }
> print @x;

print "The length of \@x is ", scalar @x, "\n";
print "The contents of \@x are", map( " '$_'", @x ), "\n";



John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall

Re: empty array?

"Ela" wrote in
news:fto18u$cht$1@ijustice.itsc.cuhk.edu.hk:

> Could anybody tell me why @x in the last line contains nothing?

You could figure that out your self, you know.

> $filename = $ARGV[0];

use strict;
use warnings;

my ($filename) = @ARGV;

> open(FP, $filename);

open my $FP, '<', $filename
or die "Cannot open '$filename': $!";

> @x=();
> @y=();
> $i=0;

my (@x, @y);

> while ($line = ) {

while ( my $line = ) {

last if $line =~ /^\s+$/; # end the loop
# if there is nothing
# but whitespace

> chomp $line;
> @words = split(/\t/, $line);


I don't know if you are expecting more than two tab separated
fields.

my @words = split /\t/, $line;

> $x[$i] = $words[1];
> $y[$i++] = $words[2];

Is $words[1] an error or did you really mean to refer to the second
element of @words?

push @x, $words[1];
push @y, $words[2];

> }

Anyway, here is a revised version of the program that does away with
$i. Also, I replaced @words with two scalar variables: No point in
putting the other fields in @words if you are not going to use them.

#!/usr/bin/perl

use strict;
use warnings;

my (@x, @y);

while ( my $line = ) {
last if $line =~ /^\s+$/;

unless ( $line =~ /^[^\t](?:\t[^\t]+)+$/ ) {
warn "Fields are not separated by tabs:\n'$line'";
next;
}

my (undef, $wx, $wy) = split /\t/, $line;

push @x, $wx;
push @y, $wy;
}

use Data::Dumper;
print Dumper \@x;

__DATA__
1 2 3 4 5 6
a b c d e f
alpha beta gamma delta epsilon zeta

C:\DOCUME~1\asu1\LOCALS~1\Temp> t1
Fields are not separated by tabs:
'alpha beta gamma delta epsilon zeta
' at C:\DOCUME~1\asu1\LOCALS~1\Temp\t1.pl line 12, line 3.
$VAR1 = [
'2',
'b'
];



--
A. Sinan Unur <1usa@llenroc.ude.invalid>
(remove .invalid and reverse each component for email address)

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