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Subject Author Date
compare array element Rose 02-21-2008
Posted by Rose on February 21, 2008, 10:28 pm
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 I find the following codes will give match for 'C' to '-', what's the
problem?

$preseq = "C-";
@preseq = splilt '', $preseq;

$curseq = "--";
@curseq = splilt '', $curseq;

$len = @curseq;
$len--;

if ($preseq[$len-1] == $curseq[$len-1]) {
print "P:$preseq[$len-1]\n";
print "C:$curseq[$len-1]\n";
}




Posted by Bob Walton on February 21, 2008, 10:51 pm
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 Rose wrote:
> I find the following codes will give match for 'C' to '-', what's the
> problem?
>
> $preseq = "C-";
> @preseq = splilt '', $preseq;
>
> $curseq = "--";
> @curseq = splilt '', $curseq;
>
> $len = @curseq;
> $len--;
>
> if ($preseq[$len-1] == $curseq[$len-1]) {
------------------------------^^
> print "P:$preseq[$len-1]\n";
> print "C:$curseq[$len-1]\n";
> }

One problem is you are using the numeric comparison operator "==" where
you should be using the string comparison operator "eq". The "=="
operator coerces both arguments to numbers, which means 0 for strings
that don't make sense as numbers.

HTH
--
Bob Walton
Email: http://bwalton.com/cgi-bin/emailbob.pl

Posted by Gunnar Hjalmarsson on February 21, 2008, 11:01 pm
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Rose wrote:
> I find the following codes will give match for 'C' to '-', what's the
> problem?
>
> $preseq = "C-";
> @preseq = splilt '', $preseq;
>
> $curseq = "--";
> @curseq = splilt '', $curseq;
>
> $len = @curseq;
> $len--;
>
> if ($preseq[$len-1] == $curseq[$len-1]) {
> print "P:$preseq[$len-1]\n";
> print "C:$curseq[$len-1]\n";
> }

The problem is that you ask for help with debugging, while you haven't
first asked Perl for help by using strictures and warnings.

Add

use strict;
use warnings;

to the beginning of the script, and make the adjustments needed to get
rid of possible error and warning messages.

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

Posted by Rose on February 22, 2008, 12:14 am
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Thanks to both Bob Walton's explanation and Gunnar Hjalmarsson's critics. I
feel very sorry for raising such stupid questions although I am very
hopeless to be ordered to learn several languages at the same time. I will
pay more attention to use strict and use warnings next time



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