Perl script for creating two arrays

Question

Input: A list of numbers on command line

Output: Two lists of numbers ,one with input numbers that are greater than zero and one with those that are less than zero (Ignoring zero valued numbers)

here is my code

#!/usr/bin/perl
$i++ = 0;
$j++ = 0;

while ($number = <>)
 {
        if($number<0)
          $first[$i++]=$number;
        else
          $second[$j++]=$number;

 }

 print "The numbers with value less than zero are\n";

  foreach $number (@first)
     print $number;
print "The numbers with value greater than zero are\n"

  foreach $number(@second)
     print $number;

I am getting the following silly errors which i am not able to rectify.The errors are

divide.pl: 2: ++: not found
divide.pl: 3: ++: not found
divide.pl: 5: Syntax error: ")" unexpected

Can anybody help me out with rectifying these errors please? I am new to perl script

You're not quite clear on whether you want to read the numbers from command line arguments (i.e. ./test.pl 1 2 3 4) or from files given on the command line (what your code currently does), using standard input if no files are given. — Chris Lutz
– Chris Lutz, Commented Oct 18, 2011 at 18:32

Keith Thompson · Accepted Answer · 2011-10-18 18:31:04Z

6

Curly braces on compound statements are not optional in Perl.

Your statements:

$i++=0;
$j++=0;

don't make sense; you probably just want to delete the "++".

You're missing a semicolon on one of your print statements.

Once you've got those problems fixed, you should add

use strict;
use warnings;

after the #! line. This will introduce more error messages; you'll need to fix those as well. For example, you'll need to declare your variables using my().

answered Oct 18, 2011 at 18:31

Keith Thompson

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3 Comments

gogo Over a year ago

but its not identifying "use". Giving an error saying use not found

TLP Over a year ago

"Giving an error saying use not found" is not any perl error text I am familiar with. Perhaps you should do an exact quote instead of a paraphrase.

Keith Thompson Over a year ago

Did you add the "use" on the same line as the #!? Don't do that. Line 1: #!/usr/bin/perl. Line 2: use strict;. Line 3: use warnings;. (I usually have a blank line after the #!, but that doesn't matter.)

TLP · Accepted Answer · 2011-10-18 19:09:36Z

2

The code you present will hardly compile. Loops should have {} around the main block, arrays are better created with push (or unshift), you should use strict and warnings, and you can't do increments at the same time as assignments (e.g. $i++ = 0).

use v5.10;
use strict;
use warnings;

my (@first, @second);

while (<STDIN>) {  # <STDIN> clearer than <> in this case
    chomp;
    if ($_ < 0) {
        push @first, $_;
    } elsif ($_ > 0) {
        push @second, $_;
    }
}

say "Numbers less than zero:";
say "@first";
say "Numbers greater than zero:";
say "@second";

edited Oct 18, 2011 at 19:09

answered Oct 18, 2011 at 18:43

TLP

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9 Comments

gogo Over a year ago

how can i do this thru command line? lik ./divide.pl -1 1 2 3 4

TLP Over a year ago

Replace while (<STDIN>) with for (@ARGV). And if you do that, you can remove chomp.

gogo Over a year ago

thanks a lot. This post helped me achieving what i needed. :)

TLP Over a year ago

@gogo You might also consider using while(<>) and using a file with the appropriate numbers, separated by newline. This will also work with STDIN if you do not supply arguments to the perl script.

TLP Over a year ago

@gogo Oh, just noticed you want to ignore zero values. Then you need to do elsif ($_ > 0) instead of else. Because otherwise else implicitly means elsif ($_ >= 0).

|

Nathan Fellman · Accepted Answer · 2011-10-18 18:31:34Z

2

I don't know what $i++ = 0 is supposed to mean, but change that to $i = 0 to initialize the variables.

Also, the first thing yuu should do in the while loop is call chomp($number) to remove spurious newlines - 5\n is not a number and treating it as one will confuse perl.

Once you've fixed that, post any new errors that show up - I don't see any other problems though.

edited Oct 18, 2011 at 18:31

Nathan Fellman

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answered Oct 18, 2011 at 18:29

Dan

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1 Comment

gogo Over a year ago

divide.pl: 2: =: not found divide.pl: 3: =: not found I am getting these errors nw and also the syntax error of ")"

mfollett · Accepted Answer · 2011-10-18 19:08:09Z

How are you executing this perl script? Beyond the errors mentioned about the code itself. It looks like you are attempting to evaluate the code using dash instead of perl.

The errors you should be seeing if you were executing it with Perl would be like:

Can't modify postincrement (++) in scalar assignment at /tmp/foo.pl line 2, near "0;"

But instead, your errors are more in line with what dash outputs:

$ dash /tmp/foo.pl

/tmp/foo.pl: 2: ++: not found

/tmp/foo.pl: 3: ++: not found

Once you've verified that you are running your perl script properly you can start working through the other problems people have mentioned your code. The easiest way to do this is to run it via perl divide.pl instead of whatever you are doing.

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